Getting these warning in log:

[Server thread/WARN]: Couldn't create template entity of bosses_of_mass_destruction:obsidilith (class net.minecraft.class_1297)... Defaulting to empty
[Server thread/WARN]: java.lang.NullPointerException: Cannot invoke "dev.onyxstudios.cca.generated.GeneratedComponentContainer.get$bosses_of_mass_destruction$event_scheduler()" because "" is null
[Server thread/WARN]: Couldn't create template entity of bosses_of_mass_destruction:gauntlet (class net.minecraft.class_1297)... Defaulting to empty
[Server thread/WARN]: java.lang.NullPointerException: Cannot invoke "dev.onyxstudios.cca.generated.GeneratedComponentContainer.get$bosses_of_mass_destruction$event_scheduler()" because "" is null

Full Log: https://paste.ee/p/0ZBus

Thank you for reporting - was this just at server startup?

It was when launching Minecraft through MultiMC, I didn't launch a server but perhaps a mod I'm using has some server properties?