Minecraft 1.15.1 internal server lag

Severe lag while playing in singleplayer.

Framerate is good and tps too (18 chunks loaded) but for example when i break blocks they reappear out of nowhere. Same for entities wich are very laggy, mobs are literally teleporting themselves.

This has not previously happening in old versions of the game, I recently tested on 1.14.4 and got no problem with this issue.

 

I also tried to only load 4 chunks but got the exact same issue.