Description of the Bug Encountered
With WIlder wild on any version since 4.0, my moded Minecraft server can't start due to registry errors.
The server work fine with previous versions installed and also work with newer versions of FrozenLib and Trailier Tales.

Steps To Reproduce

1. Install Wilder Wild 4.x + on server and it's dependencies
2. Start the server

Expected Behavior
The server should launch properly

Logs
https://pastebin.com/JirBYFbL

I see no evidence pointing toward WW being the issue, and nobody else has had this issue either.

For what it’s worth, I use Wilder Wild server-side on 1.21.4 with no problems, even with a substantial amount of other mods.
Try making a server with just WW / Fabric API / FrozenLib. It’s very possible another mod is actually causing the problem, which you may need to find through trial-and-error.

Ok,

So after testing for half a day for potential mod conflict, i've found the cause of my issue, and it's not a mod.
So it seams that my world itself cause the crash with the new version of Wilder Wilds.

So if either i create a new world with 4.x of WW (including with all mods that i already have on my modpack) or if i just don't update WW, everything works fine.
But there's a slight issue with crating a new world ...

I'm trying to find tools to see if i can "clean" my world of potential data that would cause the crash, but technically it's still due to something that changed in the code of WW on the 4.X updates.

Not really, still would have to be some strange mod conflict of sorts leading to the world issue. You can’t know / assume Wilder Wild is the one actually at fault unless you find the other mod involved in the issue.

Are you using WW 4.0.9?

@Rebel459 i've run a test with only Wilder Wild intalled on the server witjout replacing the map and the crash / bug still occured so i can confidently say : "Something with the WW update make my server not run".
That somthing might be (and probably is) due to another mod (or more annoyingly some removed mod) but the result is the same, i can update every mod on my server BUT WW.

@AViewFromTheTop Yup, I'm running on the latest version of WW (and Frozen Lib) each time i run the test.

If that can help, here a full server log from start to crash :
fullServerLog

Unfortunately that solidifies this as not being our issue…
A similar thing happens with Abnormals’ library once you remove it, it bricks your world permanently because it does some random ungodly thing with worldgen. One of many, many reasons I don’t support them.
The logs you’ve shown here are 1:1 that exact issue.