I've seen ignitions on gas engines cause issues on Spektrum radios but never noise off of a glow engine. I'm not saying that it can't happen though.

Still, I would look for some other possible causes. Could vibration from the engine be affecting the switch, a connection or something else? Do you have the antennas from the two receivers oriented perpendicular to each other? Is it possible that there is a problem with the receiver itself? Could you have a bearing or something failing in the engine to cause an unusual RF problem?

Did you try re-binding it?

If in doubt, call Horizon. They have great support for their products. Even if you have to wait for a receiver repair or something, it is better than losing a plane.