When fighting the Ender Dragon while using Progressive Bosses alongside MmmMmmMmmMmm (Dummmmmmy), the game crashes as soon as the dragon’s fireball attack deals damage.

The crash report indicates that Dummmmmmy is trying to encode a damage type (dragonBreath) that isn’t found in the registry.
Crash log is attached below 👇🏻.

crash-2025-09-06_21.08.59-server.txt

100% their issue. Encode only fails when a mod does not register a damage type. You have no idea how many mods didn't update to 1.20 properly