Hi Frank,
I just have a view on your video
https://youtu.be/2RHfv8xpqlE?t=758
There are the blank lines in RX, but imho this is OK, since the trx is not able to transmit and receive in the same. The device just properly shown T when there was an transmit and not able to receive.
If you see the exact moment when it happens then press right mouse and copy with exact position.
In my case, I was not able to receive, since the device has continuous reboot, when touched serial port communication. It has shown serial number of device for sec then freq and reboot again. (in windows)
The device have 5v from usb and 12v from power supply. It requires internal logic to switch between 5v and 12v in case of transmit.
The route cause, why it is more power hungry when I try to use serial adapter is unknown to me.
It would also require to have a look on sw, to understand.
Basically it should act as an arduino with serial (rs232c) to usb conversion. I just assume that affected circuit of power amplifier cause reset of microprocessor operation. For sure it was more power hungry, even my usb 3.0 port was not OK with it in windows once.
If you have some hamradio colleague with soldering, then give it a try. He can resolder back original part back, if it was not the case.
But I think that with probability of 80% you hit the same error which I have had in the past.
And one additional check. I just try it on my trx in Linux yet:
I have disconnect RF board and try to change freq in linux wsjtx and it works.
So maybe the quick test, if just work with mainboard and disable are transmits, then you should be able change the frequency without the problem. DO NOT TRANSMIT !
If change of frequency in wsjtx would work, without problem/restart, then you can focus on replacement fault part. You will know that problem is not in your main board.
Your problem would be imho in FDT86256 . (if you had the same problem like me in the past)
Ps: Hams, if you see any risk to do so, please add your recommendation.
// Maybe I will give a try on Windows later on. But now I plan to go ski today and enjoy.
Juraj