Disconnect the receiver from the servos before flashing!!!!!!
I have just bought a new Taranis X9E transmitter and as it came with LBT FW on it and all new receivers have LBT on them, I decided to upgrade my fleet to the new FW.
I did the first one out of a model so I could see what I was doing and it worked fine. Being lazy I didn't disconnect the servos' for the second and have toasted something in the radio!!!
Investigation shows that a track in a ribbon cable has gone and I am hoping that is all, won't know until I find a replacement.
To appears to work, but can no longer power the external module. I suspect the current draw from the connected servos did the damage...
SO the moral is disconnect servos before flashing FW to receivers!!
Regards
Paul