He just turns to his side and looks like he tries to rub, but then doesn't scratch against the rock.
My wife was saying the same thing saying he's stir crazy being in QT so long and that I sold his "friend" rabbitfish. He's been like this ever since I sold my rabbitfish. He spazzes and has smacked the mesh net a few times (He stopped hitting the top when I replaced it with a glass top) . My water parameters are super clean with very low nitrates and 0 ammonia.
I'm honestly at a loss at this point with him. He started acting like this when I started selling his "friends" when I was downgrading my tank.
Doing the fenbendazole would be good for your peace of mind but as I said above I don’t see true flashing. I think so the bath, observe for a week and see what happens. He might also have irritation from copper that is healing.