I've had my chin for about a week. I got him from a pet store (I know, groan, but there weren't any adoptable in my state that I could find). He seems pretty happy, running in his wheel and climbing into my hands any time I open the cage, but he just started pushing himself against his cage corner, standing against the bars with his head pushing through them, and just sits there. There's nothing by that side of the cage, and it's not like there's anything on the other end that he'd be running from. He doesn't chew on the bars. Is this a sign of a health issue?