Plutonium

This issue (with the sensitivity), in my experience, tends to happen when your mouse's polling rate is really high (for CoD anyway). I used to have it on 1000hz and got the same glitch but at 125hz it works perfectly fine. Changing it depends on your mouse's software but there are some programs out there that allow you to change it for any mouse.

Here's a good website to check your polling rate quickly, just click and move your mouse really fast back and forth:
https://zowie.benq.com/en-us/support/mouse-rate-checker.html

Literally one day it started working. I don't really know why or how I made it work. I'm sorry I couldn't be of more help but maybe this will be picked up again by an admin or member of staff. I tried my best to document everything I tried.

EDIT: If you're on Windows, maybe try adding all Plutonium/BO2 folders (namely %localappdata%/Plutonium) as exclusions in Windows Defender.