You are looking at the bag of your dreams, it has the perfect shape, color, length of the strap and exactly the number of pockets that you have come up with ... but ... why this zipper is jammed in the middle and it also falls apart ?! Damaged!
It is not broken at all, this slider appearance means that the bag is first of all brand new, secondly the manufacturer has allowed you to decide in which direction the bag or its pocket should open. It is your first move in a given direction that will decide which direction the slider will be sliding from now on, it is worth being aware of this possibility, because in many situations it is simply practical.
Of course, not all bags need to have sliders set up, as for those that are on display usually the seller has already decided on the opening side, often customers check how the sliders "walk". Sometimes manufacturers to avoid the vision of a "broken" slider set them up when packing.
I hope that next time you see such a slider, it will not be an obstacle to buying your dream bag!
Kasia