Your screenshot (even the first one) shows that passengers are following your waypoints. The problem only happens when they go into the real jetway and it's likely because you haven't set a custom jetway root floor height, as explained in the manual, Page 72, the chapter named "Custom Jetway Floor heights"
When there's no custom jetway root floor height set in the airport profile, GSX will assume 4.60 mt, which is the height of the default jetway, so if your model is not of the same height, you must set a custom root in the airport profile for each different jetway model you use.