My save game is about 615MB. Since a few days, I am experiencing lagging/stuttering in case of entities and orders I made.
In like every 30sec, the creatures will stop for 3-4 sec, and then they are moving forward, like nothing has happened. The orders I gave, like destroy a block of grass, or opening a chest will not be done, just after this 3-4 sec delay.
The new games, or other, smaller saves(from my kids) seems  not to be affected.
There is NO heavy redtone system, and the bug occurs even if I leave the area I built by 1000 blocks.
I tuned down the settings, to 60 FPS, 5 chunk, and every possible graphics setting turned off.
The laptop I play was able to run the game with 100 FPS with 30-40  chunk distance, as it specs are the following:
i7-9750h(6 core, 12 Threads, 2.6/4.5GHz),
2*8GB Memory,
1660Ti 6GB, and
980 Pro M.2 NVme SSD.
Every thread is working, as it should. The dedicated GPU is running, while I am playing Minecraft.
Here is a Youtube video about the bug:
https://www.youtube.com/watch?v=1NK3GE4j1MU