Originally Posted by
Tartan
Check the quilts where you got the wavy borders for bias edges. If you have bias edges along the sides, it is easy to stretch them when you put on the borders. Starch the fabric well and if I think the edges of my blocks may stretch, I do a row of stay stitching around the quilt edge before sewing on the border. It also helps to put the quilt top on the bottom so the feed dogs ease in more fabric when sewing the border on top.
I don't make larger quilts anymore but I did what Tartan stated. I first check that my quilt is square. Once I have measure, I pin. At the half way mark, at the quarter mark, at the eight mark. Marks on both border and quilt top and I match them as I pin. I make sure that the border is exactly where it should be. I never used a walking foot and never used starch back in the 90s. If I thought something might be out of whack, I would run an 1/8 of an inch stitch to make sure every thread stayed in place. Good luck. If you have to rip, then do it gently because whatever caused this problem will increase with severity if you are not careful with your thread removal. Take your time. Good Luck