lvspark

I do not have a common ground wire from my rc gear to my av gear.
The case is grounded to the power supply ground. Meaning that the transmitter case acts like a wall the rf will not pass through very well. The transmitter case is probably grounded by the nut that holds the power connector to the case, and also probably soldered in several places at the circut board level, and at the internal voltage regulators if yours has them.. You could connect you main li-po ground to your AVTX li-po ground. Probably won't make much difference since the rc Rx case is probably plastic, and I have never had to do this with avtx stuff??? Would just add to the wire mess as well.

2 different rx's and same type problem would point me to bad rx design, or avtx malfunctioning. Although, if you are using the same rc tx, that could also be the problem.

I would change out the RC gear to different brand tx and different brand rx and try that with the avtx in opperation. If you still glitch, all fingers would be pointing at the avtx as the problem.

Alternative would be if you are using the same rc tx, try a different one rc tx with the same rx and see what happens. Its either the rc tx or a bad av transmitter.. Process of elimination will eventually find the problem if you don't have proper test equipment.

Good luck!