Have you ever had a skirt that starts showing signs of stress in the rear seam? This happens with loose-weave fabrics. You may see more of this with the fall plaids.
Continue to gently pull seam allowance outward until the seam allowance looks like the skirt back used to look.
With a hand needle and thread from your sewing kit, use a running stitch to tack down seam allowance to skirt back. Use small stitches. Because of the loose weave of the fabric, these stitches will not show. Once you have secured the seam allowance to the skirt back, you can also sew through the lining for extra strength.
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