Minecraft version & Mod Version:
1.18.2
1.1.20
Single player or Server: singleplayer

Describe problem (what you were doing / what happened): started up the modpack without changing anything in it and got the error:
"roots classic encountered an error during the sided_setup event phase java.util.concurrentmodificationexception: null"

Crash log (if any):
https://pastebin.com/TeGRfGhs

(If this is a suggestion and not a bug report, delete all this and just write your suggestion!)

sorry about bad grammar and stuff, i'm not smart.

Have you tried re-installing the modpack?