I would suggest you put at least a 1 or 1-1/2" finished border on your quilts to stabilize the edges. Be sure to measure through the center for top and bottom and again for the sides. I fold quilt in half, mark with a pin, and again in half, on either side of that center pin. I do the borders the same way.
I'm so sorry this happened to your quilt. I quilt on a 9" throat DSM and haven't used a long arm. I hope this helps.