Merc Left Mouse Skill Shots Not Working

Any skill shot bound to LMB isn't working.

Grenades equipped to RMB, Mousewheel and anything else work fine, but Frag shot, Galvanic shards etc. will not shoot at all, regardless of what they're bound to. Re-selecting them on LMB or any other binding will cause the character to quickly (far too quickly) do the reload crossbow animation, but then the ability cannot be shot.

This started happening after trading items with another player (in case relevant).

Have tried everything I can think of - rebinding, resetting all input and control commands, travelling to different areas of the game, logging out/quitting and reloading etc. Nothing works. Super confused, so unless it's a weird bug, my merc is now a lemon. Any suggestions would be great!

There is something jank about the whole crossbow thing, it's like they have added extra mechanics for it that can cancel things out, if had it where you are left clicking an attack and it's just constantly cocking the cross bow, it also seems to cancel out of things if you dodge roll causing you to re cock the xbow again (even though you just did it before you rolled)