When using threads that modify shared data which is "global the the entire process", there needs to be some kind of locking mechanism. A thread has to acquire an "exclusive write lock" versus its other "thread peers" in order to update that commonly shared information. I don't see any locking code that would adjudicate write/read conflicts amongst its peer threads. It is possible that one thread might read a variable during the writing of that variable by another thread.

I don't know much about the server software that you are using, but I'm sure that some other Monks do. However, unlocked shared variable sounds like a likely suspect to me.