Ford Repair: 2003 Expedition Moonroof Misaligned, water trough, moon roof

Question
I have a 2003 Expedition and the moonroof is not closing properly.  It seems to open fully without issue.  However, when I go to close the roof, the right (passenger) side of the glass panel gets ahead of the left side.  As this occurs, you can hear gears slipping in the drive mechanism.  By the time the panel is approaching the closed position, the right side looks correct and the left side is still open about a half inch.  From this point on it has difficulty sealing tightly without some manual assistance.

It appears to me that the left side drive mechanism has some striped gears or other issue. I say this because it is possible to slide the left side of the moon roof back and forth a little less than an inch by pushing on it with my hands.  The right side, on the other hand, appears to be tight and can not be moved as much as the other side.

I have had the moonroof glass panel out and I have observed the operation of the machinery enough to know that the tracks and shuttles appear to be intact and operating properly.  On the other hand, I am fairly certain that something is wrong with the drive mechanism.  Especially the drive gears.

I want to know that if I bother to remove the headliner and access the drive mechanism, am I going to find any serviceable parts, or will this be in the replace-the-whole-moonroof category?

Answer
I have fixed many of these, as well as Explorers. Usually break something in the moonroof mechanism. Most common is the water trough at the rear breaks, either both sides or one side. Makes a lot of noise, and most times won't allow correct operation. Check at the rear of the moonroof, just under the glass for the water trough. Put the moonroof into vent and you should be able to see or feel this trough. The other breakage is in the side pieces that connect to the metal linkage. I haven't seen  many moonroofs fail other than this or a bad motor. The motor drives cables to move the glass, so the only gears are where the motor fits into the moonroof. I suspect something plastic has broken and is causing binding and noise. Sometimes the trough comes loose completely and stays behind in the roof.