Mouse sensitivity changed?

If I play a shoot game and I'm (for example Fortnite) and just looting or running into the zone, then my mouse is running as it should be. But as soon as a bit of action comes into play and I'm fighting, then my mouse keeps dropping out for a short time (as if I would lift the mouse for a short time and put it back on the mouse pad). I've also bought a new mouse to see if it's up to me, but it's not. The problem is still there. I would be very happy about a quick response, because I'm also a streamer and so can't gamble well.

Have you ever tested another USB port on the PC? Time taken a mousepad (mousepad, wood, paper)?