Often, damaged texture or entity files cause errors only under certain circumstances, such as with a certain version or in a certain level. Eliminate the entities as suggested and try again. Of course, it could also be an engine bug - but then it would since long have been also encountered by other people.

With the simple methods suggested, finding where a crash happens - in the script, the level, an entity, or the engine - is normally a matter of 10 minutes and much faster than posting or discussing here.