I was able to trace the problem somewhat. Is anyone else running multiple instances of the same server binary?
When I created a copy of the server for each instance the problem went away 100%. If two of the three servers run the same binary, one of them fails with this issue. It looks like it has to do with a resource being shared between server instances. (@SeanL: I will try to get an example for you but it may be difficult because while this issue only happens for me with multiple server instances, it also didn’t show up until I added a server RPC function).