I've been using HH blinds since before they had zippers on the windows. I've never had a problem or heard of a problem with the zippers. The blinds are hand made and sewn by individuals so I suppose things like that could happen but If there ever was was a problem I know the folks at Northwoods would fix it, they stand behind their product.
They are always striving to improve their blinds. The new ones have a heavy duty boot along the bottom edge that is an improvement over previous blinds.