If antenna wire has been shortened for any reason, that will affect range. Check for any cuts or nicks in antenna wire especially close ro the rx. If any of the wire strands in the antenna wire have been cut, that can affect range too. Make sure its not getting pinched anywhere either. Buy and install a failsafe!! You got lucky this time - next time it could be an expensive crash that stops it.

I had same trouble with mine - was overhead powerlines - interference. My prob didn't get solved until I converted to FM system.