This bug is rediciolous. When I do not move my Mouse then the game runs fine with 144FPS on my 144 Hertz monitor. Though, when I start moving my mouse in any situation (looking around or interacting with the UI) then the whole game starts lagging. Before 1.18.12 I did not have this problem but since then this problem occured.

This bug MUST be HIGH PRIORITY as it makes the game unplayable.

Also here is a recording of me playing on Cubecraft and experiencing those lagspices. Note that this happens in singleplayer. My renderdistance was 5 chunks at that time and antialiasing at 1. Please take into consideration that for you it might not seem that bad but when playing on a 144 Hertz screen this is really annoying and (almost) unplayable.

Proof:

https://youtu.be/jNFKqq7Nuhk

https://youtu.be/WnIF23JNfs8

Edit:

(In Main Menu, is the most noticeable):

https://youtu.be/OjFxRu4W1pE