Started happening after a while of the server running. When any player joins the server crashes with stack overflow.
Crash report: https://pastebin.com/av9qabpv
Log: https://pastebin.com/sEsWeVTy

Should be fixed in the next update?

Can you reproduce this without quark? I don't think it's a quark issue, quark's mixin doesn't do anything that would cause this.

I'll try. It seems to be incredibly inconsistent

Haven't been able to get it without quark yet but when we got it with quark, removing it from the mods resolved the issue. After readding quark to the mods the issue didn't reproduce.