Good day I'm new. I have a 2010 Scenic 111 1.9DCI. Everything works fine except for one annoying fault. On longer trips, the airflow through the interior vents intermittently stops working. I can hear the fan but the vents close off. This seems to be speed related, so I am wondering if the increased air pressure into the car somehow closes off a vent or flap in the system? Since it is only there on longer trips, computer diagnosis does not seem to be an option. Any experienced this?