Have you raised the equal feed attachment. I can't remember if it is possible to leave it down with the darning foot on but that would certainly stop it moving. I seem to remember when I used the 1471 for SITD the quilt kept pressing the buttons and changing the settings so you also need to watch that if you solve the other problem. It can be very confusing.
I assume you are using a straight stitch - sounds stupid but it could be that simple. I bet when you find the reason it is very simple and you will kick yourself.