attempting to start a server (1.12.2) with a few mods, simply jetpacks included. it's throwing an error on multiple server jars, so i'm tearing my hair out a bit trying to figure out whether it's an issue with cauldron or another mod
modlist:
https://kurousagi.pw/xd/feeULSj.txt
catserver log:
https://kurousagi.pw/xd/OKE9RMM.txt
magma logs:
https://kurousagi.pw/xd/K72fnCo.txt
everything works fine when removing simply jetpacks

Check this out, it may solve your issue 👍
https://github.com/Tomson124/SimplyJetpacks2/wiki/Common-Issues#server-crashes

Most likely an issue with cauldron, as unfortunately Cauldron breaks a lot of mods that hook deeply into Minecraft/Forge. Can you try starting a normal forge server with the exact same mod list to see if it works in a "vanilla" Forge environment?

Hi I work with the guy who created this issue, I can confirm that I was able to successfully load up my game and create a world in single player with the modpack with Simply Jetpacks

server starts with "vanilla" forge version 1.12.2 - 14.23.5.2854 with the previously posted modlist

If you were to try an and older version of the mod, maybe back one version, and it works then, I might be able to fix it. If not, our entire code base is not compatible
-StormedPanda

Give it a try, and I'll see what I can do
-StormedPanda

will post again after the process is complete

I'm about 100 mods in, and I can confirm that the following mod causes a crash.
https://www.curseforge.com/minecraft/mc-mods/librarianlib
https://github.com/TeamWizardry/LibrarianLib

This library is required for
https://www.curseforge.com/minecraft/mc-mods/random-psideas
https://github.com/Kamefrede/rpsideas

latest.log without LibrarianLib:
https://kurousagi.pw/xd/EP8mgbb.txt

latest.log with LibrarianLib:
https://kurousagi.pw/xd/YVl6LOH.txt

crashreport with LibrarianLib:
https://kurousagi.pw/xd/XS6Xyg6.txt

Our ASM doesn't even touch that method, so I'm not sure what would be the issue. Also, LibrarianLib for 1.12 is no longer being actively supported, though we will still try to fix any critical issues.

Unfortunately, a Cauldron ASM incompatibility isn't likely to be classified as a critical issue, especially considering the time and effort required to diagnose and fix it.

I will try to look into this.

im getting the same error have tried with 3 Forge + Bukkit server softwares, all given me the same error

https://github.com/magmafoundation/Magma/issues/256

i have updated Librarianlib from 20 to 22 and still getting same crash

LibrarianLib for 1.12 is no longer actively being updated outside of critical issues. So unfortunately it seems liblib is going to be incompatible with cauldron servers.