I don't know if this will help, but I was having issues with various functions not wokring with LPX. I ended up flashing the FP16 back to 2.02 and now everything works perfectly.
It seems like the UC / Firmware updates beyond 2.02 break the Faderport's Logic Pro x 10.5.1 functionality - but with 2.02 all features work correctly.
Including Solo clear, the panning functionality (from both the parameter knob and the fader 'Pan' function)
The process that fixed it for me was :
- reset factory settings on the Faderport 16
- download UC 2.9.2 (the ''About Universal Control' shows version 18.104.22.168805 built Oct 19,2018)
- update firmware to v2.02
Then power cycle the unit.
Then select Logic mode.
Again, power cycle the unit.
Now it's working perfectly again.
I hope this helps!