Sounds like you got a loose connection in transmitter's battery tray. Those FlySky radios are some of lowest cost, if not the cheapest radios out there. Every once in awhile one will be DOA from all the stories I hear. Normally they work fine. I had a FlySky transmitter fail on me after about a month of use. The trigger potentiometer quit working. Quality assurance is just not there. Get in touch with Redcat. They might hook you up with a new radio if indeed there is a problem with the radio straight outta the box.

If I had to take a guess as to why two different transmitters, running change in production.