I've only been able to reproduce that crash by preventing FLHook writing to it's log file(s) so far. However the main hook log (which is the log used in the crash you've shown) is not as prone to this as some of the other logs. Can you make sure that there are no problems writing to the logs? There is not quite enough error handling in some places when it comes to file I/O which will need to be addressed.
Also you said you tried to buy the "player faction ID" - do you literally mean the ID that says "player faction ID" on it or do you mean the IMG player faction ID? I've noticed that if multiple instances of flserver are running, the IMG player faction ID can show up as an ID that says "player faction ID" instead. If you do somehow have multiple instances of flserver running, that could also be causing file handle issues and contributing to the crashes.
