Keybinds change randomly in a match

My keybinds change randomly inside the match, sometimes they work, sometimes not (even in the same round). I spawn, they work, i die, respawn, they dont. Doesnt matter if i set it to mouse or keyboard, sometimes its just the standard layout and next time its mine. 

Edit: its mainly about mousebutton 3 and 4 (which are used in browser for back and forth), sometimes they work and sometimes they dont, i want to use them for gadget and ammo box (or whatever it is) so replacing keyboard 3 and 4...