Firefox 48, sometimes it is not possible to minimize the browser via titlebar

Firefox 48 from rapps,
sometimes it is not possible to minimize the browser via titlebar.
ros logs with high probability then

(ntoskrnl/mm/ARM3/virtual.c:4675) Failed to insert the VAD!

But I am not sure, whether that logging is related.

I think it's more probable for the minimize-problem to happen after the application has been minimized and restored beforehand at least once.
0.4.14-dev-1320-g3c585d0_minimizeIssue.webm
0.4.14-dev-1320-g3c585d0_minimizeIssue.log

We noticed this bug the first time, after we fixed CORE-8808, not sure, whether it points to some bug in the fix, or whether it is a completely unrelated issue.