I spent a large part of my career doing problem solving in IT software (for good or for bad, I was the one that got called when nobody else could solve it) - I learned early on that if I couldn't recreate something, I most likely was not going to be able to solve it either. So at this point I think I'd just march forward, but keep an eye on things to see if it ever changes again.
I know you know that I keep all my zone setups in a spreadsheet starting this year. There is a tab for every date I make a change, and the changes are color-coded. Yep, I'm a data nerd like that. But even with all that careful tracking, I was wondering why one of two identical zones wasn't watering the same way. Went in and looked, and it had been set from Lots of Sun to Mostly Shade. And I knowingly wouldn't have done this. Don't have a clue how I did it, but I'm pretty sure I obviously did it myself!
Sorry for the long winded answer. Couldn't help myself!