I had to put binding on my first quilt, which was for a double bed. A friend who has been quilting for 40 years told me to put a chair next to the machine to support the quilt. I would bet that would work also for straight line quilting, so the quilt does not weigh down and distort the sandwich. PS - I have a kitchen counter with stools which are almost the same height as my machine table, so it is great to support the quilt, no matter what you are doing with it!

if they serviced your machine correctly, my bet would be that the quilt is not supported and it is pulling. I have a fairly large table but I set up an extra tray table just to make sure the edges don't slip off.