We are running TFS 2012 Update 1 Patch 1 and have noticed in several projects we have some Sprints that display irratic/bad burn down charts. some appear to change every time you click on them. Yet the Sprint burn down charts displayed in SQL Reports appear to be correct, or at least consistent.
One peculiar thing I've noticed is the sprints that have bad/inconsistent burn down charts displayed in TWA the sprint contains several WI's with state "To Do" yet sprints that appear to have good/accurate/consistent charts ... all WI's reflect state "Done". Not sure if the problem is related to this or not?
Please see below post for additional info and chart examples.