This is a very well known FSX bug that doesn't have anything to do with our software or your install. FSX controls the jetway animations, and this doesn't always work with some airplanes, and the wheels sink into the ground.
Nothing we can do to fix it at this time, we'll eventually have our own custom jetway system, but until then, we are in the hands of FSX and its bugs. The same problem happens even with default jetways on a default scenery.