Devs I've had this annoying bug happen to me in the most critical moments when I'm in the middle of a firefight with hostiles:

I'm fighting some enemies and suddenly my weapon swaps from main weapon to signature weapon, which have the effect that I cannot hide behind cover, or jump away if being attacked. Instead it takes 3-4 seconds for the signature weapon-animation so I can manually switch back to my main weapon and be able to hide behind cover, and I've lost count on how many times I've died during that short sequence because I can't take cover due to the unintended weapon-swap. This is extremely frustrating!
So PLEASE devs, take a look at this and fix it!
I know it's a bug because I'm not even touching the other weapon-buttons (or the mouse wheel) and I'm using a cable-mouse.