I did bind FrSky S Bus receiver (XM+ Micro) with my Frsky Taranis X9D+ after flashing LBT firmware (for EU users) both to TX and RX. It was just needed for binding.
I don't think there is anything wrong with firmware on receiver transmitter if it's binding fine. I am flying XM+ just fine, there is no erratic behaviour related to that receiver.
It's probably your calibration, or configuration on either end. Check calibration, did you move the sticks as asked by the wizard ? Are your channels on Taranis configured in mixer to output to separate channels ?
Receiver firmware matches the X7 firmware ?
He would not see any movement if not bind, and it would not bind if firmware mismatches.