: Pulling or stretching the fabric while sewing the zipper in can cause it to "wave" once released.
: High heat from a dryer can cause the cotton tape around a zipper to shrink while the rest of the garment does not, leading to a puckered effect. Fixes and Prevention: bulve.zip
In fashion and sewing, a "zip bulge" is a common issue where a zipper does not lay flat against the body, causing an unsightly curve or bump. : Pulling or stretching the fabric while sewing