Works great on clients crashes on server.
Pastebin
irontanks: 1.11.2-2.0.0

Thanks @SFort this is a known, but undocumented (until now) issue. I haven't split out the sided items so the server is trying to render gui items (and thus, crashing).

Thanks for reporting this. I'm still working through some rendering glitches in a local fork which includes this fix. Maybe I'll push it up with the rendering glitch just to fix the higher priority error.

1.11.2-2.0.0.alpha-2 includes this PR.

https://minecraft.curseforge.com/projects/iron-tanks/files/2468052