Here is what I think on that count...

If your sales volume is cruising along at the rate that keeps you on a 3-monthly reporting cycle then your sales sag so you drop back onto a 12-monthly reporting cycle then suddenly you will see defects showing up from 12-moths ago.

Conversely if your sales pick up again then suddenly those older defects should disappear off the radar.

In our case tho we are maintaining the 3-monthly cycle.