Hello nathan ^^ .
When I restart the server. NPC's with the trait "hat" , turns back to "Spell hat unknown" .
What can I do?

Regards!

I just tried this myself to make sure it hasn't broken and it seems ok. You are trying to put a hat on an NPC, right- not give them the hat spell?

If so, then

/trait magic
/mtrait hat wool

Should do it, that'll put a wool block on their head. Is that what you were doing?

Yes, I use .
/ trait magic /mtrait hat wool
by the moment, dont have problems right now when I reboot. So.. maybe was an a bug .
Thank so much ^^