APM 2.6 and Mission Planner 1.3.35

Hello. I was wondering if anyone out there could help diagnose a Mission Planner problem for me. I have flown 3 missions with my Quad. The first was flawless. Unfortunately, #2 and #3 ended in catastrophy. They were all identical missions. My quad flies very well and has been set up to the best of my ability. I am using a Turnigy 9X Tx. I power everything with a 4s lipo. On all missions, the voltage never dropped below 14volts. The quad takes off perfectly, flies to first waypoint, then to second waypoint. After a programmed 10 sec loiter it crashes to the ground like a duck shot out of the sky.

This would not bother me so much except for the identical mission flew perfectly the first time. I never lose my GPS fix and like I said, the voltage is good. Any suggestions? I am new to this. The telemetry log shows no problems until it falls from the sky. Where should I start looking for answers?

Thanks so much. I am having such a blast with this whole autonomous thing but can’t afford too many more high speed gound collisions!!! :confused: