Just a FYI for others that may experience the same problem. After setting up camp yesterday, while opening the sliding door, something long fell off the vehicle and onto my head on its way to terra firma. It was also slightly bent, likely the last time the door was closed. It turned out to be the dust/water seal attached to the sprinter sliding door opening on top. It seemed to be mainly secured with friction, although there are traces of caulk in the track. I was able to straighten it out with some tools and reinstall it, but I'll have to get another from the factory since I trust it much less now. Your milage may vary, but it's worth taking a look to see if yours is still firmly seated to the body if you have an older AS model.
With a 2 year old AS, I clearly didn't expect this.