It does look weird to me and i am sure someone might have the same problem/advantage regarding all the latest and initial Panda algo sweeps in SERPs.
The site in question was hit on the 24th of February first and got buried on the 12th of April when UK traffic died. All of the competitive search positions were blown off the first page and settled on 2nd and 3rd which killed all the traffic.
Ok, now, I am talking about the WMT average position reports. I tested all the filters and date ranges and noticed a significant drop in impressions and clicks but... Out of 4,987 search queries in the WMT report (Web-United States), most of them kept top 10 positions with some insignificant shifting on a daily basis (up and down 0.something) I have been monitoring these since February. The reports for the UK traffic are different, the Average positions were down but as of today, showing top 10 again.
I know there could be glitches in WMT but showing unreal reports with gains and looses for 4 months.... This site looks great according to WMT but we are still 80% down.
I am curious if this observation could be explained.