As the title states, the compatibility section of the mod's jar has a class file (CRTRewards$3) which attempts to pull information from an incorrectly spelled file of CraftTweaker. I've checked, and it's spelled correctly in CraftTweaker. This causes a crash any time you attempt to load a world with a prestige reward that attempts to give you a potion effect.
crash-2021-06-30_13.09.00-server.txt