Yes it could be and it depends on what receiver it is. I have the DX6i which uses the new DSM technology and I read on Horizon that there was a number of glitching problems that were caused by the antenna being routed the wrong way out of the receiver. The solution was to re-route the antenna and it would be fine.
I don't know enough about the Super Cub to say. What does the antenna look like? Is it a small short piece of hard wire that can be bent around or is it a long soft wire?
Have you checked the other things I mentioned??