It's quite straight forward, Place end stone, Place dragon egg on top of End stone, Right click to begin Hatching process aaaaand Crash
Something worth mentioning, the first crash happened when I placed the dragon egg on top of end stone, on Ars Nouveau's Archwood forest Biome, I do not know how the breed system works, so I have no idea if it contributed to the crash
Second time it happened was on a Flat world for test, this time it was as the tile mention, Egg+End Stone= Crash, no ''Biomes" on flat worlds.

Crash-Logs UwU

First Log (My main world)
2023-09-22-1.log

Second Log (Test world try)
latest.log

Forge 47.1.43
Minecraft 1.20.1
Latest mod version
Small question, Can the dragon sit?

This should be fixed in version 1.2

This should be fixed in version 1.2

Nice!