I've messed with these door latch modules a lot when I was shaving my door handles. I had to replace the two on the driver’s side b/c they were sticking but from the handle rod, not the unlocking rod. If you want to get to the bottom of it without dropping a ton at the dealer I would remove the panels of the affected doors, and even a door that is working for reference. You will notice that there are two rods leading to the module (black box containing the latch for your door, and levers to receive the rods from the unlock switch and door handle). Hit your unlock button with your fob and see how the unlock rod will shift in your good door. Go to the affected door and feel that same lever and see if it is at least trying to throw the switch. Then remove the module by the 3 torque head bolts next to the latch, the rods simply pop in their holes 1/4 of an inch and will be easy to pop free from the module. Even if you take your time this will take you all of 15 mins to get out. I would take the good one out too so you can see how the switches throw so you have an idea what they should feel like.
If they stick you will have to buy new ones, they are one complete unit, and run about $100 ea. But better then the 500 the dealer would charge you.
Good Luck PM me if you run into a snag
