P5 loops if there is any contact with the collision object before the draping/animation begins. If you have her sitting in a chair, do you have the cloth reading both her and the chair as collision objects? If so, that could cause a loop. Think about it: "Oops. Hit the chair; better go up--Oops!" You can check for pre-drape collisions by turning on Pose room collision detection, then Property tab detection for the Body&children and the dress. Use the bottom setting for the doc window button (Show Intersections), and you'll get a black figure with red where things go bump.