Why is the zip is curved / humpy after stitching continuous zip chain to the product?
Spiral / coil zips have an S twist and Z twist in the teeth creating a ‘smile’ or ‘frown’ appearance when the teeth are joined. The left and right teeth should be both in the same direction/condition. If this is not the problem, check the sewing tension is equal on both sides of the zip.
Why are there stain marks to be found on the fabric adjacent to the zip?
Check for any solution / sprays / polishes being used on the zip teeth. Check for any excess oil being used on sewing threads if sewn application or check temperature of heat seal if sealed zip application.
Why are there stain marks to be found on the leather adjacent to the zip?
Check for any solution / sprays / polishes being used on the zip teeth. Check for any tanning chemical residues on the surface of the leather. Check that the zip has been ordered with Protecto Treatment to prevent any reaction of the pigments In the leather with the copper of the zip.