When logout from FP a client exception occurs (for about 1 second) with the following Log Error visible in the footprints.log file :

Error: Failed to execute 'send' on 'XMLHttpRequest': Failed to load '/api/portal/setlogouttimer': Synchronous XHR in page dismissal.
at ctor.start (/app/triton/app.js?_dc=20190816115458:1:218261)
at ctor.request (/app/triton/app.js?_dc=20190816115458:1:227333)
at _onViewportBeforeUnload (/app/triton/app.js?_dc=20190816115458:1:3084519)
at ctor._doLogout (/app/triton/app.js?_dc=20190816115458:1:3083211)
at ctor._logout (/app/triton/app.js?_dc=20190816115458:1:3083116)
at ctor.fire (/app/triton/app.js?_dc=20190816115458:1:183837)
at ctor.dispatch (/app/triton/app.js?_dc=20190816115458:1:519001)
at ctor.callParent (/app/triton/app.js?_dc=20190816115458:1:125453)
at ctor.dispatch (/app/triton/app.js?_dc=20190816115458:1:520809)
at ctor.b.doFireEvent (/app/triton/app.js?_dc=20190816115458:1:519941)|

This error happens when using Google Chrome 78.0.3904.108 and above

This is the result of a deprecation of "Synchronous XHR in page dismissal" in Chrome, and their progressive end of support for it.
Apparently after version 80, this will be completely retired.

This is also related to defect DRZNZ-14007
 

Solution :

For the time being, we can reactivate this option in the browser.
access the hidden options of Chrome by typing this in the URL
http://chrome://flags



Then search for the word "XHR" on the page.
Change from "default" or "disabled" to "Enabled" and then restart the browser after cleaning up the browser cache