Chances are you bought someone else's radio problem. Your choices are limited.
1.Send the radio to reliable shop for checkout
2.risk another plane with radios you don't trust
3.Scrap radios
Whatever you do, do it with Tx and Rx since you don't know where the problem is. If you send it in, be sure to give good description of what happened so they know what they are looking for.
Nothing irks us techs like a complaint like: Don't work too good. Clear as mud.

Sorry for the loss.
Kinda thought something had happened when I was reading the other thread.[]

This is ONE of the reasons I won't buy used gear.