Only when you create a new box and name it as well as when breaking a box and attempting to pick it up. I assume especially from reading the modlist that the reason is because it attempts to add something to the world or check something straight after it is created or something idk. It works fine after restarting the game and looking at it again, but I hope this is something you can fix, otherwise I'll pester the clockworks team who seem overworked enough ahaha

crash-2024-09-23_06.34.56-server.txt
Here's a crash report. Maybe have the dimension persistently exist like the nether is? Idk

Edit: I never explicitly tested if it is valkerian skies, I just know everything works fine once it is deleted or disabled. Its really annoying when I lose my stuff cause of it tho