I agree it is probably a problem with the wiring harness. Last time I fixed one I couldn't find where to buy one. Had to make it myself. If you make one be sure to get the wire that is very flexible and not the standard plastic insulation. I tried the standard plastic and it wasn't flexible enough for the movement of the helicopter. I forget the material that the insulation was made of in the wires I used but it was very flexible. I also agree it's a fun game. The one I fixed was my Uncles and I look forward to going over there all the time to play it.
Edit: I think it was silicone insulation but not sure.