The HVAC controls on the 05 to 08 are a disaster. The control unit's are steady wth the circuit board failures. Being they are setup for dual climate controls, my guess is there are separate actuators for driver/passenger.... but with how unreliable the head units are - it's probably that turd that's at fault. You will need the FSM for this level of troubleshooting but it might be just as easy to find a good used control unit and try that first. Or send it to Panasonic through Subaru and get it rebuilt. Alternatively get a JDM HVAC unit with a DIN stereo slot and just upgrade the whole mess.
GD