Chunks consistently failing to load, causing extreme lag

Today I loaded up my survival world to go visit the new Trial Chambers in some new regions I haven’t explored before.

Unfortunately, after I got maybe 100 chunks away from my spawn point, I started to get these constant errors saying that chunks have failed to load. When this happens, I also get severe lag: mobs don’t move, I can’t eat, place/break blocks, and any block updates don’t happen.

ADDITIONAL INFO:

• This world was created on Bedrock (Xbox One S) during Update Aquatic (1.13), and was transferred to Java after the notorious October 5th 2022 Xbox Bedrock update, which made it unplayable (just wouldn’t load)

• I backed up the world, so I have a copy in 1.20.5.

• This error has never happened to me until today when 1.21 came out.

Any help is GREATLY appreciated!