As the kid of a potato farmer, I am going in my memory way-back machine, and my hypothesis is the potatoes were not harvested correctly. We used to kill the vines 2-4 weeks before harvest to force the sugars in the spuds to convert to starch. It also hardened the skin to protect from blight and make the potatoes easier to store and handle after harvest.
It's possible that these potatoes were harvested too soon so there was low starch, high sugar and high acid.
Certain varieties of potato need the set time in the ground more than others. We grew Sebago and Kennebec from PEI seed potato stock and they definitely need ground cure time, if I recall correctly.
