Observer fires when it should not

Studio-side

1. create a custom document type named documentTypeA
2. create a custom document type named documentTypeB
3. in Designer generate the forms
4. in creation form of document A paste the following:

   <!--
   `nuxeo-documenttypea-create-layout`
   @group Nuxeo UI
   @element nuxeo-documenttypea-create-layout
   -->
   <dom-module id="nuxeo-documenttypea-create-layout">
     <template>
       <style>
         *[role=widget] {
           padding: 5px;
         }
       </style>
       <nuxeo-input role="widget" value="{{document.properties.dc:title}}" label="Title" type="text"></nuxeo-input>
   
       <nuxeo-input role="widget" value="{{document.properties.dc:description}}" label="Description" type="text"></nuxeo-input>
   
     </template>
   
     <script>
     Polymer({
       is: 'nuxeo-documenttypea-create-layout',
       behaviors: [Nuxeo.LayoutBehavior],
       properties: {
   
         /**
            * @doctype documentTypeA
            */
         document: {
           type: Object,
           observer: '_observeDocA'
         },
   
       },
       _observeDocA: function() {
         console.log("observer type A")
       }
     });
     </script>
   </dom-module>
   
   

5. in creation form of document B paste the following:

   <!--
   `nuxeo-documenttypeb-create-layout`
   @group Nuxeo UI
   @element nuxeo-documenttypeb-create-layout
   -->
   <dom-module id="nuxeo-documenttypeb-create-layout">
     <template>
       <style>
         *[role=widget] {
           padding: 5px;
         }
       </style>
       <nuxeo-input role="widget" value="{{document.properties.dc:title}}" label="Title" type="text"></nuxeo-input>
   
       <nuxeo-input role="widget" value="{{document.properties.dc:description}}" label="Description" type="text"></nuxeo-input>
   
     </template>
   
     <script>
     Polymer({
       is: 'nuxeo-documenttypeb-create-layout',
       behaviors: [Nuxeo.LayoutBehavior],
       properties: {
   
         /**
            * @doctype documentTypeB
            */
         document: {
           type: Object,
           observer: '_observeDocB'
         },
       },
       _observeDocB: function() {
         console.log("observer type B")
       }
     });
     </script>
   </dom-module>
   
   

6. save the project

Server-side

1. create a workspace
2. open google inspector
3. in google inspector click the console tab
4. in google inspector clear the console logs
5. in webui click the + sign and select documentTypeA
6. observe the console logs show observer type A
7. close the form and observe another line showing observer type A
8. click the + sign and select documentTypeB
9. observe the console logs show observer type A and observer type B
10. close the form and observe another line showing observer type B
11. click the + sign and select documentTypeB again
12. observe the console logs show observer type B and observer type B (see consoleLogs.png)

Expected behavior: the observer should be triggered only once when opening the form and only the right one (observerDocA for type A and observerDocB for type B)