This seems oddly similar to discussions my wife and I have about what we're going to have for dinner... then we're not, then we are.
I used to see that odd up and down pattern before I learned about the Authorized User All Zero penalty. I was an authorized user on spouse's Chase credit card. Chase reports the balance at statement close and again if the balance reaches zero before the next statement closes. If an AU balance showed on my reports, then there was no score penalty. If it droped to zero, then a -8 penalty until a non-zero balance reported with the next statement. At that point, it would go back up 8 points. Once I learned about the AU All Zero penalty and how Chase cards reported multiple times, we learned to always allow at least one AU balance to report, but to make sure that it wasn't with a Chase card (we use Amex cards for this purpose).
