I'm sorry about the length and lack of clarity of this post!!!!
I received a phone call from the owner of the dealership a couple of days after the useless visit to them to try and have them diagnose and fix my Sedona's Power Sliding Door problem. He was making sure that I'd give them an "excellent" review if I receive a survey. He told me that if didn't give him full marks, he'd lose a lot of money.
Well, I decided to tell him how unhappy I was with his service department's attitude and inability to diagnose the problem. He asked me to give him a second chance and to make things right (but not to give him a negative review on any survey I might receive). So, I think I'm going to take it into him again next week.
This evening, I spent 10 minutes or so trying to find out what causes the sliding door not to close properly, and I think I can replicate it now (maybe we all can!). It appears as though it has nothing to do with the vehicle facing up or down a slope. It is the angle at which the vehicle is leaning (left or right) that determines whether the door will have a problem or not. Try and picture this... If the door that is having the problem is leaning into the van (it is at the higher end of the slope) or ]\ (The backslash is the passenger door and the right square bracket is the van), then the door won't close properly (even when it's at a very slight angle).
I usually park my van facing towards the street at the edge of my driveway (where the driveway seems to have a slight incline), so when I look at the van from behind (from my garage), it appears to be leaning slightly to the left (towards the driver's side). The lean (although minor) is enough to cause the passenger side sliding door not to close properly.
Please would someone try and confirm that the problem is due to the vehicle leaning left or right?