Here's one that you might not think of. I started with a JR 662 and during training it got pulled off of the bench onto the concrete floor by the buddy box cord. Everything looked and worked Ok and I just got a small scratch on the housing. Well about a week later, I was setting trim for the day since we had increased the flying speed that I was getting used to. I trimmed a little down to keep the plane flying pretty level. Did it a couple of times when I became used to the trainer wanting to climb at higher speeds. Well, at the end of one of the flights (actually it became my last for a while) I began to trim the elevator back to a more up position. The trim switch would only work moving the elevator down. My instructor saved the plane by doing tight circles at the end of the runway till he got it down. Found out later from the mfgr that the trim switch for the elevator had slipped out of position when the radio fell to the ground and it would only trim down. If you don't send it in make ABSOLUTELY SURE that you have checked EVERYTHING before assuming no damage was done.