My flask hotkeys forcibly changed today??

I logged in to play a quick session, and for some reason, one of my flasks got its old hotkey back. They used to be QWERX, but I unbound all of them but one due to being automated, and I made the last one Q to fit my other ability sequences better. And so I played like this for weeks...

Then just this morning, my 4th slot got the 4 hotkey without me doing it?? And I can't unbind it by swapping it to something and then replacing it. The game will not allow me to unbind my 4th slot!!

What's going on??