Mod v. a5.0 to a.5.1 crashes servers. Tried Forge versions 14.23.1.2585 and 14.23.1.2555 with and without other mods, but it gives an error. If I run the mod on client, it works well. Here`s a report.
crash-2018-01-07_23.30.43-server.txt

Thanks for the bug report. It looks like an issue where one of the software components Avatar Mod uses on is broken on servers. I'll take a look at it.