I cant upload the world due to the size limit on this site so i had to upload it to google drive.
and as i commented 2 years ago my swamp was probably made during 1.14.
I did try to update the world to 1.21.3 but the issue remains.
Tried to kill all entitys using /kill @e but the issue remains.
I seem to be able to recreate the issue by creating a new world with the same seed: 6222775103534946325 in 1.14 and then run it in the latest version of minecraft (1.21.3)
Swamp cords: X: -480 Z: 320
https://drive.google.com/file/d/1KyAY4Fhr0kJ1XgPSJEyeTIE7tsF8oKfc/view?usp=sharing
I got the same issue. My world and this swamp was generated in 1.14
Issue still remains for me i tried to make a new world again in 1.14 with the same seed and let it load for 5 min and afterwards i ran the same world in the latest version and 32 on both render and simulation let it load for 5 min then i ran the command you sent and were also in creative mode but i saw no progress even after letting the game be in the background for hours.