2x Fs-a8s From banggood problem

I bought 2 flysky fs-a8s From banggood on separate occasions. Both will not communicate with the flight controller. But it works fine with a irangex ir-a8s receiver which is a rebranded flysky fs-a8s. The video shows that the irangex irx-i6x transmitter binds ok with all three recievers (showing a solid red led when bound) but only the ir-a8s will output signal to the flight controller. I feel i have 2x faulty flysky receivers