Forge 12.18.1.2011 NMSOT v1.1.6 crashes server, probably need to build against 1.10.2 or 1.9.4, not sure if 1.9 is compatible with the later versions.

https://gist.github.com/Keridos/cf932c8d28619f88608f18739e9089ab

The error is very unspecific so it may be very well a compatibility issue between this mod and another one. I can confirm though that removing NMSOT it no longer crashes the server with that stacktrace.

EDIT:
Wait, let me test it. Actually I build it against forge 2018 for 1.10.2. It may be not compatible with 1.9 but should compatible with 1.10.2
Thanks for report.

After rough tests, I found it is compatible with 1.10.2, 1.9.4, not fully compatible with 1.9 (failed on some feature, but will not cause crash).
I can not find any clue indicates my mod crashed the server. Need more information to investigate this issue.