I rented a longarm once and this happened. It started out at first working fine then after a couple of feet it went wacky. the top looked great and I had no idea. It was because there was lint in the bobbin they said. Even when they came and changed the bobbing they did not check it. They were very nice and did not charge me for the time on the machine. They suggested washing it because that often makes it sink into the fabric. They offered to pick it out for me if that didn't work. It was not perfect after washing it but was much better so I just left it. Too long a drive (3 hours) to go back for that. If you paid for that, I would certainly take it back!!! I know how sick I felt after seeing mine come off but no charge for it did help the sick gut feeling. It was not something on a time line though. The quicker you take it back the better.