Plugins Installed:

Spigot 1.12
Vault https://ci.md-5.net/job/Vault/
UltimateChat-1.8.8-b196-Universal.jar
DeluxeTags
PEX

First There is my error: https://pastebin.com/EKiACCKR

After a few test to try solve that, I deleted Uchat and DeluxeTags and Vault, to reset config, still have the problem. So i decided to turn off plugins One By one to looks where it come from, after disable Vault, the error was gone. Si i try some other Vault plugins ( Maybe that one was broken) but still have that error even wioth differents Vault plugins.

If Someone know the source i will be gratefull.
Thanks