+ AA6YQ comments below
This may not be a Flex related problem. I see something like this once in a while with my Icom 7600 on FT8. The symptoms are the radio goes into transmit but no tones are sent—to me that seems to implicate WSJTX. While I think it only happens on a new QSO initiation, it is so infrequent that I haven’t been able to figure out with any certainty the pattern to when/why it happens.
+ I've also seen that with my 7800. The radio switches from RX to TX, but no tones are transmitted.
+ Bill G4WJS, is there a way to identify the cause of this behavior?