RE: RE Synth problems...
Take the same set up (RE tx) but without the speed controller. Replace this with a servo. If the transmitter is faulty then you will see some crossover with right stick. The servo that replaces the ESC will twitch or move. If this doesn't occur, the Tx is not directly causing the problem.
However, You have an eclectic mix of products from many different manufacturers. We tend to take it for granted that all these items will automatically work together, but it is not always so. Personally I suspect that the ESC could be the problem, simply because I have had exactly this problem. I had an ESC which I could not get to work with one TX, but it worked perfectly with another.
Tryb the experiment above and see what happens.
Regards,
John.