Had a pretty rough go of it today. We were flying at 8-10 feet today, doing a little tuning in stabilize mode. Craft was looking more stable than it ever has. Entered forward flight, came to a stop in a hover at about 8 feet. Suddenly craft pitched back oscillated heavily for a bit, then crashed upside down. In the Log it says ERR: RADIO-2. It also FSed into land mode, which is what crashed it. Was working on PID settings to transfer to the other flight modes. I cant find any information as to what ERR: RADIO-2 means. The ArduPilot wiki shows an error 0 and 1 for the radio subsystem. Any help would be greatly appreciated.