For those still looking for a solution to this problem, I may have found it.
A couple months ago, I was doing some work on a buddy's car, and his servo lead and switch harness was beat up and damaged. He had also been experiencing random glitches, and an External BEC had been helping. I replaced his servo lead and switch harness, soldering new wires into his RS Pro [out of warranty], and then forgot all about it.
Until today, I had my RS Pro apart to clean out dust/dirt from the case and get everything cleaned up to start building a new touring car. Close examination showed a kink in the signal wire [white wire] where it comes over the top board before exiting the case, and at this kink, the wire was very weak. The switch harness was kinked over even more, with the insulation getting very thin.
I replaced the servo lead and switch harness on my RS Pro in the same way I did on my buddy's, and then remembered I'd done this before, and gave my buddy a ring.
Since I replaced his servo lead and switch harness, he's been able to ditch the external BEC, and run his antenna inside the body racing outdoors again, zero glitching. It will be a few more weeks before I can test my RS to see that it's fixed my problems as well, but it all points to the same causes.
In both cases, I replaced the servo lead with a "heavy duty" 20ga lead, instead of the 22ga stock lead. I also replaced the switch with another micro switch that can be disassembled to get to the solder points [which I can't seem to do with the Tekin switch], so I can use 20ga wire on the switch as well. You may need to open up the hole on the case to fit the extra bulk of wire a little easier.
A thin pencil soldering iron is needed for this, as well as a steady hand and good soldering practices. A light scrape is needed over the solder points to remove the board's epoxy coating, and extra care must be used to make sure there are no solder bridges between the connections, as all the contact points are very close together!
I've also talked with Tekin about this, and [can't remember the guy's name] they agreed that if the kinked wire damaged the wire strands, it could very well limit current delivery to the RX, especially on the switch harness.
Since I've only had this problem with my older RS's, I'm leaning toward the belief that this is an age-induced problem, but easily remedied if you're handy with a soldering iron.
Hope this helps some of you guys still struggling with this issue.