Mouse Sensitivity

This has been going on for a while now for me, but it appears that this was an issue back in 2013 even, and yet there's still no solution to it anywhere I can find.

For those who don't know what I'm talking about, my mouse sensitivity changes from 7/11 to 5/11 whenever I begin loading into a game. Happens regardless of mouse I'm using, and happens on my laptop's trackpad as well.

Does anybody have a solution to this?