That makes sense, so I looked at the Arduino sketch that sends the POZYX data to the Pixhawk, The function send_vehicle_position (line 430 of https://github.com/ArduPilot/ardupilot/blob/master/Tools/Pozyx/IndoorLoiter/IndoorLoiter.ino appears to send just vector distances in the form of x, y and z relative to the 0,0 beacon. There is a YAW adjustment in the Pixhawk, but I think its just determining the angle of the vector relative to North. I did not recognize any instances of inertial or heading data being fed to the Pixhawk.
Maybe the Yaw variable I set in the Pixhawk is wrong.
Question: Is the Yaw adjustment relative to magnetic or true north?