Like I said I do not think it will be the rx but one time I was having a big prob with my radio (new out of the box) and it would do that with the engine running.. and it was a glow engine. I sent it to D and J and he said that there was no rubber gromet under the cristil. that was the prob with it.. The vibration messed it all up..

Just takeing a stap in the dark. lol

Paul