Tuner

Hi all, I have a 2016 C450 and I'm having an intermittent issue where the airflow through all the HVAC vents will drop to almost zero. I can hear the cabin blower fan is working just fine through all speeds, the cabin filters are fine, and the HVAC drain tube is clear. It switches from floor, to vent, to defrost just fine. I also noticed when I switch the driver side to full hot and the passenger side to full cold, there's only a small amount of airflow coming out of the passenger side vents and no flow from the driver's vents. When I switch the driver side to full cold and the passenger side to full hot there's basically no air flow from driver side or passenger side vents.

Wondering if anyone has any insight as to what could be the problem. Or if anyone has experienced this before. Any help is appreciated, thanks!