Help me brainstorm

I've been crashing planes and need to find where the issue is. Here is my setup.

I have 2 Jumper T8SG, v2 because my grandson and I fly together. Just to keep track, one is yellow, the other the "carbon" color. Both have been running great for nearly a year.

I have 6 operational airframes, all Flite Test or derivatives of their designs, all containing LemonRX stabilizer-plus with diversity antennae. I have 'failsafe' set on each to cut motor, go to autolevel mode with slight nose up and a fair amount of rudder.

I had been losing control at times. I determined that it was when using the carbon controller on any aircraft. I found the SMA connector loose so I opened the controller and found the ground pins had broken so I soldered the connector shell to the ground plane. I also noticed the antenna was loose at the flex joint so I replaced it with another antenna. All this under the assumption that I was losing output power, therefore, range.

I did a range test having the wife walk up the street while I walked down. She was holding one of the planes and I was carrying the controller pushing back and forth rhythmically on the aileron stick. She told me over cell phone when the control began to skip. I did the test with both the 'repaired' carbon controller and the yellow one. The skipping started at almost the same distance (within 20 feet.) I'm assuming problem is solved.

Here's where it gets strange. I take the controllers and some planes out to fly. My first three short flights with the carbon controller resulted in the motor stopping within a minute to 2 minutes. I still had all other control to turn back and glide it to landing. On the fourth flight, flying fine when suddenly the aircraft rolled inverted, nosed down and continued rolling - corkscrewing to a vertical impact.

On all those flights, I never got more than 120 feet away, if that. I'm thinking it's not a reduced range issue, as the LemonRX never went to failsafe behavior. It seems like I lost some channels but not others. Another data point: I connected the carbon controller to a flight simulator using PPM and it controls fine.

I'm not sure where to go next. I don't really understand the transmitted protocols, so I can't envision where the controls can get selectively lost.

Ideas?

i had the same problem as your.. i have 2 t8sg v2 plus.
The first one i bought from a redneck who was not able to wrap it safely..result: i received it with broken antenna where it sold to the board.. i did not saw it at first so i did programmation on remote while rf module was heating a lot until it die..
Remote was still working perfectly but range was really decrease... 50 feet and the drone was falling from sky without advertising...
I had to replace the rf module.. now work nicely

ravageur wrote: i had the same problem as your.. i have 2 t8sg v2 plus.
The first one i bought from a redneck who was not able to wrap it safely..result: i received it with broken antenna where it sold to the board.. i did not saw it at first so i did programmation on remote while rf module was heating a lot until it die..
Remote was still working perfectly but range was really decrease... 50 feet and the drone was falling from sky without advertising...
I had to replace the rf module.. now work nicely

Thanks for your answer. I do think it is the rf module. I replaced the right angle sma connector and antenna but it still cuts out after less than a minute. Rather than spend almost half the cost of the transmitter on something that "might" work, I decided to order a new transmitter.