im just going to play on my survival world then suddenly 2 error popped up in my top right screen saying chunk error while the world is still loading. then after a minute later i saw this. thank goodness i have a backup and have a comparison of original and bug. ive press optimized world but i dont know if that was the case though
MC-273816
1.21 world chunk switched
Resolved
Invalid
0
for more information the version i created the world is from 1.12.2, the i updated it to 1.20.4, then 1.20.6 and in that version i clicked Optimise World, and then 2,21 and i clicked Optimise World. like 20 rejoins later this bug occurs. the seed is 66830 in version 1.12.2