Hard to say, when you make your cheese do you use the floc method to determine when to cut? Do you measure pH levels to guide when to shift to the next phase? Do you weigh the cheese to try and get an idea of how much moisture was removed during stirring? etc. If by following the recipe you mean you do everything to the same time schedule, that could be part of it. Basically, the milk can be different each time so the same amount of rennet can work differently in the milk on the two days; one may floc a bit sooner, the other a bit later, which means if you cut after the same amount of time you are cutting at different points in the process (the cultures and rennet process the milk, so you're not doing the same thing at the same step). Tracking the pH also lets you know how the make is going and where you are in that process.
Also, of course, the aging conditions in caves, especially ripening boxes, have local variations in temperature and humidity. The aging conditions could be quite different between the two sets of cheeses.
Anyway, those are the first things that came to mind for me. I'm sure others will have more suggestions.