ok now my question is do you recognize that also when being on the desktop or in other games?
if yes, it might be the mouse or the mousemat
opticals arent picky about mousemat surfaces but about extreme colorchanges on the mousemat (print white-black and so on)
have you tried messing around with the config, eg the XY ratio?
a bad XY shouldnt cause this, but it changes the behavior of left right movement compared to up down
1,5 and 1,75 are the most common, maybe 1,75 works better for you
a question to the cod players
i always thought cod has a square deadzone?
if im right that might be the reason for why movements like diagonals feel odd