Bug when clicking on "update" in update center - Studio tab

In Nuxeo DM's Admin Center->Update Center -> Studio,
Clicking on the "update" button, then browse around in the Nuxeo instance from another browser tab, then back to the update center browser tab and click again on update: it produces the following crash.

If I open a browser (let's say Firefox) and let it on the update center page, and open a second browser, let's say Safari, and use it for testing, the crash appears much less. (could not say it will never appear, though).

On the browser's screen :
org.nuxeo.ecm.webengine.model.exceptions.WebResourceNotFoundException: No resource found at nxthemes at org.nuxeo.ecm.webengine.base.Main.dispatch(Main.java:132) at sun.reflect.GeneratedMethodAccessor924.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at com.sun.jersey.server.impl.uri.rules.SubLocatorRule.invokeSubLocator(SubLocatorRule.java:162) at com.sun.jersey.server.impl.uri.rules.SubLocatorRule.accept(SubLocatorRule.java:94) at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:133) at com.sun.jersey.server.impl.uri.rules.ResourceClassRule.accept(ResourceClassRule.java:83) at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:133) at com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:71) at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:990) at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:941) at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:932) at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:384) at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:451) at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:632) at org.nuxeo.ecm.webengine.app.jersey.ReloadingJerseyServlet.service(ReloadingJerseyServlet.java:74) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.nuxeo.ecm.webengine.app.WebEngineFilter.doFilter(WebEngineFilter.java:115) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.nuxeo.wss.servlet.BaseWSSFilter.doFilter(BaseWSSFilter.java:106) at org.nuxeo.wss.servlet.FailSafeWSSFilter.doFilter(FailSafeWSSFilter.java:42) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:83) at org.nuxeo.ecm.platform.ui.web.multipart.MultipartFilter.doFilter(MultipartFilter.java:73) at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69) at org.jboss.seam.web.ExceptionFilter.doFilter(ExceptionFilter.java:64) at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69) at org.jboss.seam.web.RedirectFilter.doFilter(RedirectFilter.java:45) at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69) at org.ajax4jsf.webapp.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:178) at org.ajax4jsf.webapp.BaseFilter.handleRequest(BaseFilter.java:290) at org.ajax4jsf.webapp.BaseFilter.processUploadsAndHandleRequest(BaseFilter.java:368) at org.ajax4jsf.webapp.BaseFilter.doFilter(BaseFilter.java:495) at org.jboss.seam.web.Ajax4jsfFilter.doFilter(Ajax4jsfFilter.java:56) at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69) at org.jboss.seam.servlet.SeamFilter.doFilter(SeamFilter.java:158) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.nuxeo.ecm.platform.ui.web.rest.FancyURLFilter.doFilter(FancyURLFilter.java:127) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.nuxeo.ecm.platform.web.common.requestcontroller.filter.NuxeoRequestControllerFilter.doFilter(NuxeoRequestControllerFilter.java:142) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.nuxeo.ecm.platform.ui.web.auth.NuxeoAuthenticationFilter.doFilterInternal(NuxeoAuthenticationFilter.java:353) at org.nuxeo.ecm.platform.ui.web.auth.service.NuxeoAuthFilterChain.doFilter(NuxeoAuthFilterChain.java:35) at org.nuxeo.ecm.platform.ui.web.auth.oauth.NuxeoOAuthFilter.doFilter(NuxeoOAuthFilter.java:167) at org.nuxeo.ecm.platform.ui.web.auth.service.NuxeoAuthFilterChain.doFilter(NuxeoAuthFilterChain.java:33) at org.nuxeo.ecm.platform.ui.web.auth.NuxeoAuthenticationFilter.doFilter(NuxeoAuthenticationFilter.java:326) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.nuxeo.ecm.platform.ui.web.auth.NuxeoAuthenticationFilter.doFilterInternal(NuxeoAuthenticationFilter.java:513) at org.nuxeo.ecm.platform.ui.web.auth.service.NuxeoAuthFilterChain.doFilter(NuxeoAuthFilterChain.java:35) at org.nuxeo.ecm.platform.ui.web.auth.oauth.NuxeoOAuthFilter.doFilter(NuxeoOAuthFilter.java:167) at org.nuxeo.ecm.platform.ui.web.auth.service.NuxeoAuthFilterChain.doFilter(NuxeoAuthFilterChain.java:33) at org.nuxeo.ecm.platform.ui.web.auth.NuxeoAuthenticationFilter.doFilter(NuxeoAuthenticationFilter.java:326) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.nuxeo.platform.login.web.LoginStackCleaner.doFilter(LoginStackCleaner.java:49) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.nuxeo.ecm.platform.web.common.exceptionhandling.NuxeoExceptionFilter.doFilter(NuxeoExceptionFilter.java:80) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454) at java.lang.Thread.run(Thread.java:637)

... and in the logs :
13:19:40,890 WARN [WebLayoutManagerImpl] Overriding definition for widget type path
13:19:40,890 WARN [WebLayoutManagerImpl] Overriding definition for widget type studio_header
13:19:40,890 WARN [WebLayoutManagerImpl] Overriding definition for widget type multiplePrefixedUsersSuggestion
13:19:40,890 WARN [WebLayoutManagerImpl] Overriding definition for widget type chainedDirectory
13:19:40,890 WARN [WebLayoutManagerImpl] Overriding definition for widget type multiChainedDirectory
13:19:41,084 ERROR [CompositionHandler] Could not get default negotiation settings.
org.nuxeo.theme.negotiation.NegotiationException: Could not obtain negotiation for: nuxeo5 (strategy) engine (object)
at org.nuxeo.theme.negotiation.AbstractNegotiator.negotiate(AbstractNegotiator.java:53)
at org.nuxeo.theme.negotiation.AbstractNegotiator.getSpec(AbstractNegotiator.java:38)
at org.nuxeo.theme.jsf.facelets.CompositionHandler.apply(CompositionHandler.java:162)
at com.sun.facelets.compiler.NamespaceHandler.apply(NamespaceHandler.java:49)
at com.sun.facelets.tag.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:47)
at com.sun.facelets.compiler.EncodingHandler.apply(EncodingHandler.java:25)
at org.nuxeo.theme.jsf.facelets.vendor.DefaultFacelet.apply(DefaultFacelet.java:99)
at com.sun.facelets.FaceletViewHandler.buildView(FaceletViewHandler.java:524)
at com.sun.facelets.FaceletViewHandler.renderView(FaceletViewHandler.java:567)
at org.ajax4jsf.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:100)
at org.ajax4jsf.application.AjaxViewHandler.renderView(AjaxViewHandler.java:176)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:110)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:100)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139)
at org.nuxeo.ecm.platform.ui.web.lifecycle.NuxeoLifeCycleImpl.render(NuxeoLifeCycleImpl.java:98)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:266)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.nuxeo.wss.servlet.BaseWSSFilter.doFilter(BaseWSSFilter.java:106)
at org.nuxeo.wss.servlet.FailSafeWSSFilter.doFilter(FailSafeWSSFilter.java:42)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:83)
at org.nuxeo.ecm.platform.ui.web.multipart.MultipartFilter.doFilter(MultipartFilter.java:73)
at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
at org.jboss.seam.web.ExceptionFilter.doFilter(ExceptionFilter.java:64)
at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
at org.jboss.seam.web.RedirectFilter.doFilter(RedirectFilter.java:45)
at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
at org.ajax4jsf.webapp.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:178)
at org.ajax4jsf.webapp.BaseFilter.handleRequest(BaseFilter.java:290)
at org.ajax4jsf.webapp.BaseFilter.processUploadsAndHandleRequest(BaseFilter.java:368)
at org.ajax4jsf.webapp.BaseFilter.doFilter(BaseFilter.java:495)
at org.jboss.seam.web.Ajax4jsfFilter.doFilter(Ajax4jsfFilter.java:56)
at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
at org.jboss.seam.servlet.SeamFilter.doFilter(SeamFilter.java:158)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.nuxeo.ecm.platform.ui.web.rest.FancyURLFilter.doFilter(FancyURLFilter.java:127)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.nuxeo.ecm.platform.web.common.requestcontroller.filter.NuxeoRequestControllerFilter.doFilter(NuxeoRequestControllerFilter.java:142)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.nuxeo.ecm.platform.ui.web.auth.NuxeoAuthenticationFilter.doFilterInternal(NuxeoAuthenticationFilter.java:513)
at org.nuxeo.ecm.platform.ui.web.auth.service.NuxeoAuthFilterChain.doFilter(NuxeoAuthFilterChain.java:35)
at org.nuxeo.ecm.platform.ui.web.auth.oauth.NuxeoOAuthFilter.doFilter(NuxeoOAuthFilter.java:167)
at org.nuxeo.ecm.platform.ui.web.auth.service.NuxeoAuthFilterChain.doFilter(NuxeoAuthFilterChain.java:33)
at org.nuxeo.ecm.platform.ui.web.auth.NuxeoAuthenticationFilter.doFilter(NuxeoAuthenticationFilter.java:326)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.nuxeo.platform.login.web.LoginStackCleaner.doFilter(LoginStackCleaner.java:49)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.nuxeo.ecm.platform.web.common.exceptionhandling.NuxeoExceptionFilter.doFilter(NuxeoExceptionFilter.java:80)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
at java.lang.Thread.run(Thread.java:637)
13:19:41,094 WARN [ThemeService] The 'template-engine' attribute in <view name="page frame" template-engine="..."> may only contain a single template-engine name
13:19:41,095 WARN [ThemeService] The 'template-engine' attribute in <view name="section frame" template-engine="..."> may only contain a single template-engine name
13:19:41,095 WARN [ThemeService] The 'template-engine' attribute in <view name="*" template-engine="..."> may only contain a single template-engine name
13:19:41,095 WARN [ThemeService] The 'template-engine' attribute in <view name="cell frame" template-engine="..."> may only contain a single template-engine name
13:19:41,095 WARN [ThemeService] The 'template-engine' attribute in <view name="cell frame" template-engine="..."> may only contain a single template-engine name
13:19:41,095 WARN [ThemeService] The 'template-engine' attribute in <view name="*" template-engine="..."> may only contain a single template-engine name
13:19:41,095 WARN [ThemeService] The 'template-engine' attribute in <view name="*" template-engine="..."> may only contain a single template-engine name
13:19:41,095 WARN [ThemeService] The 'template-engine' attribute in <view name="*" template-engine="..."> may only contain a single template-engine name