reliquary version: 1.3.3.639
so... I found out what happens (or at least can happen) when you (by removing and replacing the item) disable and reenable a zombie pigman charm when pigmen are angry: you get a null pointer exception! Congratulations! You win! Seriously though, please fix this if you haven't already.
crash-2017-05-19_21.16.44-server.txt

This is resolved in build 649 that was released more than a month ago so you just need to update to more recent version.

oh ok. Sorry to trouble you. I should probably update my mods more frequently, eh? Yeah.... the joys of being a custom pack server owner...