We have 3 completed sprints appearing in our backlog view. I have made every effort to confirm all stories have been removed from the sprint (returned to backlog or assigned to the active sprint) or their statuses set to closed. This was done by going to the sprint reports and examining each bug or story listed as "in progress" in the report. If need be, the bug or story was updated with the current sprint or status (closed), and none of them possess subtasks.
The sprints were also edited to have the correct start and end dates. While the these dates are shown in the sprint report, they were blank in the backlog view until they were edited to have them.
What else could possibly be causing these sprints to continue to linger in the backlog view?