Everytime I ADS, my sights flick unimaginably fast in another direction. Mouse sensor is fine, and in-game settings are normal as far as I can tell. Did the obvious (restarted Sandstorm/Steam/PC, unplugged mouse) to no avail.

video: https://streamable.com/7atb7

Don't know what's causing it and it only does it in Sandstorm. Can't really play atm.

Any help is appreciated. Thanks.

This is caused by your in-game settings (you may enter greater value than the slider allows).

Either try to reset them to default or locate your config directory and remove or edit Controls.json:

C:\Users\UserName\AppData\Local\Insurgency\Saved\SavedGames\Profile