tedster - 3:38 pm on Aug 9, 2012 (gmt 0)
Right now, I don't trust WMT to indicate the truth of the data ranking is calculated from. As you point out, in recent weeks all kinds of reporting anomalies are showing up. Unless you have actually seen traffic drops that correlate to the reporting changes, I'd simply set the information "on the mack burner."
Unfortunately, Webmaster Tools does go through periods where it's not very dependable as a source of data that means "take action on this right away." It seems to be based on a secondary copy of Google's data, not the actual core data used to generate SERPs. And that secondary copy gets, well, very strange at times.
It may just be caused by a reporting idea gone haywire, or a bad data import from another back end copy. However, when the WMT data gets weird, we need to stay focused on our actual traffic and treating that well well.