That sounds more like a bad scope or mounts, I'd remove the scope and base, remount the base with Loctite on the screws, and make sure the rings are tight when you remount the scope. Mounting a known to be good scope wouldn't be out of line either in the process of elimination to find the cause of the back and forth groups. Is the barrel good and tight on the frame when the action is closed, no looseness?
Tim