I have Firefox set to restore sessions upon restart. Up until a week ago this worked fine. I also use pinned tabs extensively with no problem until recently. Now when I restart Firefox one of 2 things happen. Either the pinned tabs are gone while all non-pinned tabs remain, or everything launches correctly but the pinned tabs disappear one by one (in a perfect sequence) over the course of a few seconds right after startup. I am absolutely confounded by this bizarre behavior. My computer is a Win 10 Dell desktop.