For, some reason, Primordial Caves for me aren't generating. It just stops generating and leaves a giant hole. It's kind of like when you're flying in creative mode to a biome or something in an unloaded chunk and it stops you from going any further for a second and then when the chunk is loaded it allows you to fly through it again (sorry for the awful explanation). And usually when I encounter this, on the saving world screen it just freezes. Like I can't even close Minecraft I need to restart my computer to close Minecraft. I will try to post more issues if necessary.

Mods installed are:
Alex's Caves and Citadel (Duh)
Alex's Mobs
Cloud Storage
Domestication Innovation
Twigs with Geckolib
Xaeros World Map
Zetter
And Farmer's Delight

Hopefully this helps

incompatiblity also with Etc

Update: All the mobs can't move either, so it just freezes the game indefinitely.

incompatible with Twigs

But, why only the primordial caves? I mean I've been to the Magnetic Caves and Toxic Caves and there was no problem.

dang, I loved that mod.

I just visited the primordial with twigs enabled and it works

Not to be annoying, but is there a patch for this issue coming around soon?

The few server side logs of the hanging seem to reference block collision gathering:

at net.minecraft.world.level.Level.m_7925_(Level.java:635) ~[server-1.20.1-20230612.114412-srg.jar%23347!/:?] {re:mixin,pl:accesstransformer:B,xf:fml:twilightforest:cloud,re:computing_frames,pl:accesstransformer:B,xf:fml:twilightforest:cloud,re:classloading,pl:accesstransformer:B,xf:fml:twilightforest:cloud,pl:mixin:A}
at net.minecraft.world.level.BlockCollisions.m_186411_(BlockCollisions.java:62) ~[server-1.20.1-20230612.114412-srg.jar%23347!/:?] {re:classloading}
at net.minecraft.world.level.BlockCollisions.computeNext(BlockCollisions.java:81) ~[server-1.20.1-20230612.114412-srg.jar%23347!/:?] {re:classloading}

The few mixins that both Twigs and Etcetera share in common include this mixin into blockstate collisions:
https://github.com/moddingplayground/twigs-forge/blob/1.19/src/main/java/net/moddingplayground/twigs/mixin/BlockStateBaseMixin.java#L17C17-L17C26
https://github.com/N1nn1/etcetera/blob/main/src/main/java/com/ninni/etcetera/mixin/AbstractBlockStateMixin.java#L18

This is likely indirectly causing this issue.

I'm not too sure as to what could be causing the issue in Twigs - from what I can see, it's simply checking the block that is currently in the blockstate and going from there. However, this is code from 1.19 - I cannot seem to find any repo for Twigs 1.20+, though I may be looking in the wrong place. If anyone could link the relevant 1.20.1 code that would be appreciated.

For Etcetera, the problem becomes a lot clearer to see.
https://github.com/N1nn1/etcetera/blob/main/src/main/java/com/ninni/etcetera/mixin/AbstractBlockStateMixin.java#L21-L22

if (world.getBlockState(pos.down(1)).isIn(EtceteraTags.OFFSET_REMOVER)
|| (that.getBlock() instanceof TallPlantBlock && world.getBlockState(pos.down(2)).isIn(EtceteraTags.OFFSET_REMOVER))

Right here, there is a querry being made to the level to load in the two blocks immediately beneath any given Plant block. There is no checking if these block positions are in a loaded chunk - meaning this code would force unloaded chunks to attempt to load, thus causing ticks to take too long. It would also explain why we only see this error in Primordial Caves and Abyssal Chasms - the other biomes in the mod don't really have 'Plant' blocks (such as the Ping-Pong Sponge and Venus Flytrap).

Don’t know if you already got this or I’m misinterpreting what you asked for but I’m pretty sure this has Twigs 1.20.1 code on the repository https://github.com/N1nn1/twigs

had this same exact issue and finally found this thread to solve it. I wish twigs was compatible but removing it for the massive content Alex's Caves offers is definitely okay with me.

@AlexModGuy im not sure if any of this helps, but here are tons of crash logs and pastebin crap from my issues before I found this thread: https://www.reddit.com/r/admincraft/comments/19du63g/single_server_tick_took_60000_seconds/

***Here is my most recent crash report before uninstalling Twigs- https://gist.github.com/calinado/9449906f3d703b43b5b9e9c4e5a85382

I was removing tons of mods that I thought would be causing the issue when Twigs was the culprit all along, so dont mind the dozens of removed mod errors. it basically stalled my server and Watchdog inevitably crashed everything

summarized links:
https://pastebin.com/Nxky8pZf
https://spark.lucko.me/iLNKht76kl
https://gist.github.com/calinado/e8a51c702d053c75ea572123e1043ea1#file-gistfile1-txt
[edit] the 1st pastebin link doesnt seem to load anymore.