Justin
I had a blend door problem with mine that was relatively silent and simple. The pivot pin on the blend door broke, disconnecting the actuator from the door. 1st symptom was uncontrollable HOT (Az) or cold (in the mountains in winter) air in the footwell of the passenger side. Made an occasional clunking noise when switching to recirc but relatively silent problem.
You can check by flipping the glove box down (press in by the stop on the side of the box and remove the stop cord if equipped). You'll see the blend door actuator behind (actually in front of) and above where the box usually sits. It's a metal cylinder with a vacuum hose on one end and a flat metal rod (actuator arm) extending upward to the right out of sight behind stuff on the upper end. You almost need a mirror or to stand on your head, but take a flashlight with you and look around in there, you can even see a bit of the door itself. Turn on the power & fan, rotate the air diverter dial back and forth into recirc mode and you'll see the actuator arm move, if it doesn't move you have another problem, if it moves, just follow it. Anyway, the actuator arm connects to a plastic pivot pin on the blend door and you can see/feel where the end of the actuator arm goes onto the pivot and operates the blend door. On mine, that pivot pin was broken but I was able to reposition the actuator arm onto the remaining end of the pivot pin (there was about a 1/4-1/2" of the pin still there) and secure it with a couple of nuts (8 or 10/32nd) to lock it on. That did the trick really a simple repair, just had to do a lot by feel, yoga helps too.