Q: Why does the slider slip off the zipper chain?
A slider that leaves the chain has either passed a missing or damaged stop, or the chain is too narrow at that point. The distinction decides who pays for the repair, so locate the exact exit point before touching the slider.
- Find the exact point where the slider leaves and photograph it next to a scale.
- Check both ends for a top stop, a bottom stop, or a cut chain that was never stopped.
- Measure chain width at the exit point against the maker's tolerance; a narrow chain releases the slider.
- Inspect the slider for a spread or cracked body, which lets it walk off a normal chain.
- Review the cutting and sewing operation for trimming that removed a stop.
Unstopped or trimmed chain is a garment process issue, while a spread slider or an undersize chain is a zipper defect. In either case, do not simply squeeze the slider closed, because that hides the cause and the problem usually returns within a short period of wear.