Look at the tubes and check for cracking, etc., and make sure it's not getting pinched anywhere. Also check to see if any debris is partially plugging/blocking the passenger nozzle outlet.
mine did exactly this last week. It was a chunk o white stuff in the nozzle.
I cut the soft line when I removed the nozzle as the line was pretty well stuck and I didn't want to break it. Some air from a nozzle and it's clean. Just use a vacuum hose splice to stick the softline back together and it's fixed.