Well, on a plus note. When you find a vent window replacement, it's pretty much a complete unit, rubber and all. If in fact the swivel shaft is broken, your best bet would be to find a replacement. Clean it up well and make sure you use some white grease on the lower shaft. The rubber isn't always in good shape. It's the luck of the draw.That sucks about the rubber seal because it's toast. The other side is tip top.
You can check with Kevin (O.D.Showtime). He's the best parts source on the site, and like most of us, we recommend him highly. Plus, he's one of the nicest people you'll ever deal with. 👍👍