It's not zinc rot. It's blistered plating. Plating blisters are hollow while domes pushed up by zinc rot are solid. Plating blisters result from a poor bond between the copper plating and the zinc core. Subsurface corrosion caused by contaminants trapped between core and plating are responsible for the solid domes of corroded metal. Domes pushed up by subsurface corrosion are generally larger and fewer in number than plating blisters.
I would not call that any kind of planchet error, more like poor quality control by a third party vendor(Jarden Zinc produces Zincoln planchets for the US Mint).
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