I've been there...its not fun! But my problems were self inflicted as I wanted a shorter COAX.... and didn't want to buy another AMB cable. I would check your BG noise first... its a simple thing and easily over looked. It could be something as simple as a dirty or bad BNC connector... been there. I would still test the COAX.... and check it from both ends.... Just going by the troubleshooting guild in the manual. Thats the only thing thats caused me problems.
I've heard of people having problems with the rc3... but I havent had any. Mines about 3 years old.