Front Defroster clearing passenger windshield only

It seems as if I'm not getting the same volume of air to the driver's side windshield vent as I am on the passenger's side. The passenger's side clears up very nicely but on the driver's side, I get a 1 inch strip of clarity very close to the vent.

The driver's dash and door and floor vents blow hot air. Could something be jamming that vent and if so, how do I go about diagnosing it?

I suspect you have something wedged in the pipe feeding the outlet duct or the feed pipe has come off. Access via foot well once under dash trims removed.