Repeatable crash found with projectile spells encountering Nether Portals. Recreatable in singleplayer and multiplayer. Any spell projectile attempting to travel through the nether portal causes the server (or internal server for singleplayer) to crash to desktop. No such issues with bolt spells. Crash log attached from a singleplayer instance.

crash-2025-02-25_23.21.16-server.txt

I wasn't able to reproduce this issue in testing, but I've made a change that should hopefully fix it on your end nonetheless. The fix will be available in the next release, tentatively v6.0.4.