"Help" window defrost 2009 tacoma

I have a 2009 Tacoma and the window defrost for the front wind shield now has a mind of it's own. The air still comes out of the vent but it is favoured to one side. It started dong this and majority, if not all the air, would come out of the drivers side but now it has switched to the passenger side. So half the wind shield fogs up while driving in winter conditions. Anyone else have this issue? Anyone know how to fix it?

 

I took my truck in today to have them look at the same thing. I have a 09 tacoma and the last few times coming back from snowboarding I noticed that the driver side is the only side the defrost is working on. I read some other threads and it looks like one vent in the middle is all there is. Seems like foam or something is blocking the one side. Im going to try to use some grabbers to search around in there. I really don't want to rip the dash out. Im guessing a lot of squeaks will follow