this happens once in a while when I boot the World of Dragons client.

https://paste.dimdev.org/jiyudaceve.mccrash

which is my pack ofcourse.

Install guidebook. I didn't have it installed, but a mod was trying to use it and that's what caused the exact same crash as you.

That's kind a forge issue, cos I don't control the dependency extraction, but given forge is out of support, the only solution from my end would be to release a version that shades the commons code instead of using it as a library, so that the mod doesn't rely on the dependency extraction stuff. I didn't really want to do "major" changes like that to the 1.12 version but if it's so unreliable... :/

Try using v2.9.3. It's up on curseforge already.

I have guidebook tho, that's the issue.

Try updating it.

gbook                               | 2.9.2                        | Guidebook-1.12.2-2.9.2.jar

as extracted from attached bug report. You see the version that is installed.

Have you tried downgrading it?