Visible topstitching wobble

Understitching that wanders away from the seamline, leaving the facing visible from outside, comes from sewing too fast or not keeping seam allowances pressed toward the facing. Slow down and hold allowances flat as you stitch.

Topstitching that gathers fabric into small folds instead of lying flat comes from tension too tight, a stitch too dense, or sewing bulky layers without a walking foot. Loosen tension and use a walking foot.

Seam allowances unraveling into loose threads after the first wash mean the edges weren't finished before construction. Serge, zigzag, pink, or bind raw edges before or after sewing the seam.

Lumpy, hard-to-press seams at corners or curves come from leaving full seam allowance width in places that need to fold or turn. Trim, grade, and clip curves to reduce bulk before pressing.

A facing edge that rolls to the outside instead of staying tucked inside usually means it lacks understitching or the interfacing is too light. Understitch close to the seam and match interfacing weight to the fabric.