Stuff like this is common in chain assembly. The feed for the plates misses one one once in a while, usually when the hopper is low. Most chain makers use a laser, or mechanical feeler to detect missing plates as the completed chain emerges from the assembly machine, and scrap the affected section. Some still use human inspection in the packing department, but even with the best of controls a bad chain can slip by.

While no one, even a Taiwanese maker of chains under someone else's label, wants to ship defective product, it isn't a crisis because it's assumed that the installer will catch the problem before the bike ever leaves the work stand.