I have the x4r on three of my quads. Have had little problems with any of them. I use a PPM connection on all three. The easiest way to check if it is a FC problem or receiver problem is test the motors in Betaflight/cleanflight/raceflight, which ever you use. If they spin up, it is probably not the FC.
I run the antenna’s down the inside edge of the front arms on a strip of electrical tape underneath, leaving the bare exposed part of the antenna hanging down under the motors. The props pretty much make sure they are blown away from the frame when they are spinning.
I used to use tubes and run them out the top for reception. After numerous tube replacements and a couple ripped off antennas, I made a new plan.
The only problem I have had with an x4r was a firmware upgrade needed on one of them since then. It would be hard to bind and then would unbind apparently for no reason at all. Firmware upgrade fixed it. Was probably sitting on a shelf somewhere for a very long time. Pretty solid units. Good luck.