The reason for the jittering is the GLIDE parameter. When you touch the door first you will glide to the left and then along the wall which moves you a little backwards from the door. In the next frame you will glide along the wall, then the door and thus move a little to the right.
"Falls das Resultat nicht einfach nur dermassen gut aussieht, sollten Sie nochmal von vorn anfangen..." - Manual
