At this point, my first suspect is the mode door actuator. It is mounted on the HVAC box. Check to see if it is loose.
This is the actuator/door that controls the airflow direction. Check it and let me know if everything is secure.
If you look below, I attached a pic of it. I circled it in the pic. The other actuator is the blend door actuator. Confirm both are tight.
Take care and let me know what you find.
Joe
See pic below.
Image (Click to make bigger)
Sunday, August 28th, 2022 AT 7:45 PM