I saw a couple of other people talk about this but there didn’t appear to be a resolution. Certain feeds in particular will move on their own from the feed tab to the original tab. I can duplicate the problem pretty easily in Firefox with the following example:
http://www.dailyherald.com/rss/rss.as…
All the Daily Herald links exhibit this problem. Once the issue starts, the feed ends up in the Original Tab and there is no way to get it to go anywhere else. . Even if you can catch the screen with the tab choices and in fact select the feed tab, it will just go back to the Original screen. It is like there is a backlog of left arrow key commands Once it starts doing this you have to exit Firefox and start again to get any other behaviour.