That is a great tip. I learned it from a wedding dress repair place, when I took in a rucksack for a zipper replacement, and the guy fixed it in an instant, with the same advice of “don’t over-squeeze”.

The other thing that happens often with coiled zippers is that tiny grains of dirt/rock jam the teeth in a few areas along the zipper. Best not to use Silicone lubricant, even the “dry” type (many recommend  this) as it will “invite” more particles to stick, but instead flick/shake/vibrate the area to dislodge embedded particles. Works better than using a brush (without vibration) to clean the zipper teeth.

From motorcycle jackets, I learned that despite my dislike of coiled zippers (preferring the “Vislon” molded teeth), coiled is more durable (reference). So coiled zipper are a good fit for rucksacks or concertina bags (one can avoid zippers altogether) exposed to dirt and bending.

Happy zippering.