AltGr (right alt) crouches even though I've bound it to push to talk

I've bound my AltGr key to push to talk, but when I press it in-game my character crouches instead. I've bound press crouch to Ctrl (both of the alternate keys are Ctrl, since unbinding keys is not possible), and toggle crouch to C. In the bindings menu it doesn't distinguish between AltGr and Alt, it just says "Alt" in both cases.

I've read that Windows interprets Ctrl + Alt as AltGr, but surely pressing AltGr shouldn't just inversely produce a Ctrl + Alt macro, but emit its own unique code? I don't think I've run into this in other games.