I normally don't make over three pounds of dough at a time in my KA stand mixer, but I don't see that you did anything out of order. Like Patrick, my first thought was that maybe there was an error in the amount of yeast used--much higher than 1.5 g. You didn't indicate what water temperature you used but if the finished dough temperature was in the proper range, that suggests that it was not excessively high. You would need either an excessive amount of yeast and/or an excessively high finished dough temperature to have the dough overferment in about 40 hours, especially at the temperature of your refrigerator compartment where you stored the dough balls. Of course, if your refrigerator malfunctioned and was much, much warmer than when you placed the dough balls in the refrigerator, then that could certainly cause overfermentation. But that is something you would have detected very quickly.
I don't see anything in your dough formulation per se that could cause the overfermentation you mentioned. Is it possible that you forgot the salt? Salt helps develop the gluten structure but it also regulates the fermentation process and affects the role of the protease enzymes. A dough without salt can have a lot of volume expansion initially, and quickly, but the gluten structure, which can be attacked by the protease enzymes, may not retain the gasses of fermentation well, leading to a weak, slack and sticky dough with poor structure and work-up. If you saved or can retrieve some of the dough and bake it, that would tell you whether you forgot the salt. You will taste it.