Describe the bug

Unable to load, create or re-create worlds.

Modpack version

3.8.1

Launcher

MultiMC/PolyMC

Launcher/crash logs? Errors? Screenshots? Screencaps? Any custom mods?

PolyMC is currently unsupported by FO, so test with only MultiMC. In any case, I have unarchived 3.8.0 for the time being.

I cannot confirm this issue on MultiMC with fresh 3.8.1 instance.

crash-2022-05-14_16.55.29-client.txt
latest.log

I don't have a screenshot, but when loading existing worlds; it said something like a datapack being unstable/unsupported and that i need to enter safe mode. But clicking safe mode button did nothing.

When re-creating it said it is unable to do so because of an unexpected error.

And when creating a new world, after the loading animation and 'Loading World' message, it immediately changes to 'Saving World' and gets stuck.

However, i redownloaded and reinstalled v3.8.1 and now it seems to be working on PolyMC.. :/

You are using custom mods, I cannot test all possible combinations so it is critical to mention those and test without those every time you report a bug. That's also what the initial bug report form says, I don't know why you just deleted that part...

Anyway, I'm glad you got it fixed.

Yes, i added more mods but i tried Binary Search and ended up with just the original mods from the modpack. And when the issue still persisted with just the original mods, i reinstalled it and it was still having issues. :/

When Loading Old Worlds;

When Recreating World;

When Creating New World; (No idea why it's the wrong screen... It gets stuck at 'Saving World' after immediately changing from 'Loading World')

Also, these are the mods i added ontop;

But FO doesn't contain datapacks? Ask the creator of that data pack.

Well, some mods try to catch mixin errors.. And end up in Datapack error handlers. and some datafixers seem to be broken as well as seen in java.lang.IllegalArgumentException: Data fixer not registered for: minecraft:DUMMY in block_entity. As far as i can tell, it's something related to lithium or Noise Generator at net.minecraft.world.gen.chunk.NoiseChunkGenerator.handler$ddf000$hookConstructor(NoiseChunkGenerator:599) ~[?:?]

I just tested on MultiMC.. It's also facing the same problems with the list of most i added.

Remove all custom mods and add them back one by one until you find the one that breaks it.

Yea, that's what i'm gonna do.. But it breaks the instance, even if i remove all custom mods, the issue remains so.. This might take a while.

Okay, so.. Before adding any mods, i tried adding older 1.18.1 Worlds into a new Copy of v3.8.1 and it failed to load or re-create Old Worlds. But it still can create and load 1.18.2 Worlds.

Maybe loading Old worlds is an issue with Fabulously Optimised, but getting stuck at creating new world and breaking instance entirely issue is caused by some custom mods conflict with the original ones.

I tested v3.8.0, it fails to load or recreate old worlds as well.

Are those old worlds still using datapacks (especially if it's the same one you're using now)? Because the error screenshots regarding the datapacks you posted are from vanilla.

Okay, thank god i had backup for my redstone world.. Yea, i realised they had been loaded into by Amplified Nether and Nullscape. These are the only 2 World Generation mods I've ever used. Though, except for a ModTest World, no other dimension was ever loaded in either my Survival World or the Redstone World.

I guess, these two mods had broken my worlds regardless.. Even if you don't load the Dimensions they overhaul, they still break the World if you remove them later on.

latest.log
Okay, Now it's not loading old worlds anymore (with custom mods), the backups that had never been loaded by mods.. Whereas Vanilla v1.18.2 loads the same backup without any issue. And it's not even identifying versions older than 1.14 even without custom mods.

If you are still unable to solve your issue, try the Fabric Discord https://discord.gg/v6v4pMv channel #player-support

FO should not affect the worldgen at all. If something's really wrong due to a mod it has, it may be Lithium.

Yea, but FO should identify pre-1.14 worlds?

Also, i am noticing some weird horizontal distortions in FO, but none in Vanilla 1.18.2.

Also, i am noticing some weird horizontal distortions in FO, but none in Vanilla 1.18.2.

If you can reproduce it without any custom mods, feel free to open a new issue.

I recorded a video but, it's not visible in the video.. Just on my Display, (4K@60Hz)

And yes, without custom mods..

If it's not visible in the video, it may be a driver issue which is not something I can help with. Otherwise try adjusting full screen or windowed full screen (enable the mod in Mod Menu).

But it's fine in vanilla? at same resolution so.. I don't think it's a driver issue.

But yea, turning off Borderless Mining Mod fixed it.