Windows system mouse speed automatically fluctuates between fast and slow

When playing FPS games, I am particularly sensitive to mouse speed, but the system always mysteriously causes the mouse speed to suddenly speed up or slow down (after a few days, it automatically returns to normal). I have ruled out hardware issues (both Logitech and Razer have experienced this), and the driver settings are fixed with no abnormalities. I suspect it is a Windows system bug.

I need a solution. Thank you for your response.