We also had issues with this system.
after numerous service visits under warranty, tech concluded that the root cause is the control board in the rear unit. It was replaced at the end of season. We will find out this summer if it is truly resolved. Our initial problem was front AC not turning on, and bedroom thermostat reading 5-10 degrees C (actually 25 degrees C).
FYI the thermostat talks to the rear unit control board and front unit communicates to the rear unit.