My Aternos server stop the server immediately and leave me no warnings. When I opened the crash log, the error said "Encountered an unexpected exception" and mentions "cannot be cast to ...", and "entities.ProjectileEntity" with its actions and components. Unfortunately, I haven't cast any spells during that time.

here is the crash log, see line 268:
https://mclo.gs/QWclDTt - for Spell cast