ORIGINAL: tsands
after 5 flights I think there is a very good chance your rx battery was dead. I noticed you said it was charged when yo went to the field but didn't say anything about checking them after 2 flights. I check mine EVERY flight but most check after 2 or 3. Most of mine last 2 flights but I don't have any that last 5 flights.
Your batteries are too small or possibly defective, you've got serious binding in your pushrods, or you're getting in two REALLY LONG FLIGHTS. Most setups should be able to get 4 flights comfortably. However, I'm not disputing your suggestion that a dead rx battery could have been the cause of the crash.