Error when accessing Admin Center

Caused by: java.lang.IllegalArgumentException: Comparison method violates its general contract!
	at java.util.ComparableTimSort.mergeHi(ComparableTimSort.java:835)
	at java.util.ComparableTimSort.mergeAt(ComparableTimSort.java:453)
	at java.util.ComparableTimSort.mergeForceCollapse(ComparableTimSort.java:392)
	at java.util.ComparableTimSort.sort(ComparableTimSort.java:191)
	at java.util.ComparableTimSort.sort(ComparableTimSort.java:146)
	at java.util.Arrays.sort(Arrays.java:472)
	at java.util.Collections.sort(Collections.java:155)
	at org.nuxeo.ecm.platform.web.common.session.NuxeoHttpSessionMonitor.getSortedSessions(NuxeoHttpSessionMonitor.java:149)
	at org.nuxeo.ecm.admin.UsersActivityManager.getUserSessionsCount(UsersActivityManager.java:181)