Yes, sometimes. So, to add to your paranoia, rats in extreme distress or pain will brux.
However, Badger sure doesn't sound like he's at Death's door

I've seen my boys doing it whenever. Sitting in a hidey box, on top of the sofa, cuddling on my neck, running amuck in the bathroom during playtime. I think in some cases it's almost like thumb sucking in humans - a soothing/comforting mechanism, rather than one of pure joy or sheer distress.