@EA_Blueberry
I am so happy to see a Community Manager take a look at this. I posted on it as well a few months back (I made this account just to try to raise the issue!). The new quip wheel functionality in the recent patch took away the only viable mapping we had to avoid this issue. We used to be able to map R3 to the extra character action, which was a dead button in a firefight, but now that the quip wheel is tied to the extra character action button we are at a loss again. The only viable thing to do is map R3 to fire mode - and then not use any weapons that have different rates of fire to avoid it changing mid fight.
I'm a huge fan and play all the time, have spent 100-200 dollars on the game, would kill to have a simple ability to unmap R3 completely. There is quite a bit of side chatter on this issue, it happens to a lot of us from time to time, but for some of us it's every fight, like every one.
Fingers crossed!