Why is my Minecraft mouse sensitivity in 1.8 weird and jump even though I move my mouse evenly?

In the 1.16, the sensitivity works perfectly. But since I tend to play PvP, I'm mostly on 1.8.9. But for a few weeks now my sensitivity has been strange and has been making jumps in the game. But I haven't changed anything in the settings.

This is probably a bug that occurs often. For me it helped to reduce the HZ frequency to 500