Crash on 1.12.2 server

[Gebcrafter]

I'm aware 1.12 isn't being developed, but perhaps there is an easy fix on my end for this?
Mod works perfectly fine on client. Installed on server, it won't start. Of about 250 mods, removing Horse Modifiers allows it to run.
Crash Report
It also doesn't work when just Horse Modifiers is installed.