This is pretty bad, but even worse is that I'm unable to reproduce - also Samsung S6 Edge, also 6.0.1, also SwiftKey or Samsung Keyboard.
What's the trick?
Weird. I now understand, that the menu should show up in front of the keyboard and not behind. After reading your post I tried to do some investigation on user's side:
While testing the battery got low and the device was shut down. After charging and launching the device the issue was gone. For some minutes... because:
So I tried to reproduce it and I could reproduce it:
I first disabled the Floating Action Button, then the issue appears (see steps I mentioned earlier). See screenshots
But I was not able to get rid of it anymore , I tried
- enabling Floating Action Button
- then closing/killing AquaMail
- empty cache of AquaMail
- reboot the device
No success until now