If you built a slime farm before this snapshot it will no longer work once updated. My guess is the slime chunk is actually now positioned adjacent to where it used to be.
Description from MC-186137:
RandomSeed not converted to minecraft:dimention seed from the WordGenSettings resulting in seed 0 to all worlds from previous versions
RandomSeed value is not transfered to minecraft:overworld, minecraft:the_nether and minecraft:the_end seed from the WordGenSettings resulting in seed 0 to all worlds from previous versions. It creates odd chunk generations near the borders of newly generated chunks and other issues like that.
Linked issues
is duplicated by 4
MC-186137
RandomSeed not converted to minecraft:dimention seed from the WordGenSettings resulting in seed 0 to all worlds from previous versions
Resolved
MC-186792
Slime Chunks Not Spawning Slimes
Resolved
MC-188502
Previous slime chunks are no longer valid
Resolved
MC-191061
When I type /seed the seed is 0. Is there any way i could fix this?
Resolved
Comments 14
I'm pretty sure that command is broken because it says "0". Also, my witch farm still works which would imply the seed is still the same. Or, at least it's extremely unlikely that another witch farm happened to generate in the same spot.
If /seed says 0, the seed is 0. Updating from one specific snapshot to another specific snapshot (I suspect 20w17a to be involved) reset the seed on some worlds. Unfortunately, we have been unable to figure out exactly what is causing it so far, and it doesn't seem to happen from 1.15.2 to the current snapshots. Nevertheless, I will adjust the ticket title to fit the actual issue.
Structures aren't seed-based once they've been generated. They are based on bounding boxes stored in level.dat (or somewhere)
Just tested it. It won't happen in a world created in 1.15.2 and oppened in 20w22a. Also tested negative in 20w21a and 20w20b. Tried with a 1.15.2 created and 20w20b opened world in 20w21a but still no seed resetting.
I don't know it that can be useful or if you already know that; but I fixed this problem by changing the seed in the level.dat files back to the original one (using NBTexplorer) and then i deleted the corrupted chunks using MCAselector. In this way the chunks regenerate using the correct seed.
I have a similar issue where my world had been slightly corrupted from rolling back to an older version. In doing so it caused my seed to say "0". I downloaded NBT Editor and manually changed it back. That worked fine. However when I downloaded MCA Selector and reset the effected chunks, its loading completely different chunks to what they should be. Almost as if its the wrong seed, but I'm certain its not. Do you have any ideas of what might be wrong?
Has the seed of the world changed in any of the last few versions?