The Console is being spammed like this:
"Starting initial dragon fight!
[18Jan2024 18:57:24.152] [Server thread/INFO] [betterendisland/]: Unable to find all 4 summoning crystals. This shouldn't happen!"

This started happening after adding BetterEnd and resetting the regions folder.

Back up your world, and then try using the command /end_island reset. Deleting the regions folder isn't enough to fully reset the dragon fight's state.