I have an LG G4 phone which rather helpfully has a custom clipboard widget where it will keep the last 10 things you've copied in any easy recallable list. That's all well and good until you copy something that shouldn't be remembered.
In the case of keepass, I copy a password which gets added to the top of the clipboard list - then a few seconds later I see "****" has been added to the top of the list as keepass tries to blank out the clipboard. Looking at the clipboard widget, I can still see my previously copied password there - totally visible, in plain text & easy to paste again.
There is a clear operation that I can manually invoke to flush out everything in the clipboard - but relying on users to remember to do that is unreliable.
It's also worth noting that LG in their infinite wisdom, have bundled this clipboard widget in such a way that it is impossible to disable, or uninstall or even configure. I believe there is a way to get rid of it if you root your phone - but aside from any warranty implications, I'd imagine there are also some security considerations to be had when rooting your phone.