I was flying my heli a few weeks ago when I started getting some glitching in the radio system. I landed quickly, and after checking everything over, went back in the air. This time, the tail seemed to be the problem so again, I landed and did a thorough check of the tail control system. I have a newer 401 gyro and JR 4735 servo mounted on the boom. A wiggle/giggle test revealed the servo to stop when pulling on the wire. A broken servo wire seemed an easy enough fix but on inspection it was instead a motor wire broken at the board. I repaired the wire, checked the rest and wrote it off as a bad solder.
Today, I very nearly crashed when I lost the tail while inverted. This time it was the orange signal wire that was broken at the board and the others were frayed as well as the one I had just fixed. I noticed that the board didn't fit tight in the case like most do and there was no silicon rubber holding the wires to the board and board in the case like all my other JR servos. I can only assume that the board buzzing around in the case caused the broken wires since the servo has low time and has no strain on the wire to it. I repaired the wires and siliconed the whole thing so this shouldn't happen again.
I'm not sure all JR servos have the silicone but I think it's a good idea to check - maybe it'll save a heli..
Kirk