DrropS, I'm having exactly the same problem. It's free standing and not knocking against anything but when Hoshi gets in there it really rattles. He absolutely loves it and spends most of the night in it.
It came fully assembled already so I've been trying to work out whether something needs adjusting but it seems fairly secure. I've tried tightening the bolt but doesn't make much difference. I'm wondering if I should try taking the whole thing apart and putting back together. Is it difficult to do? I'd appreciate any help, as would my upstairs neighbours probably
