A rattle is certainly not acceptable. We've only ever seen a rattle twice an alpha dog; both times caused by wires vibrating against the back of the driver. When we found this we modified our process to a) use adhesive to bind the wires to a routing the ensures they won't rattle against the driver and b) use similar bass test tones as a test during tuning of the headphones.
I don't like to speculate so we have to see the phone to be sure what's going on. PM me and we'll fix it right up for you.
Can you send me your test tuning bass tones? I want to be sure it is rattling rather than shipping from Canada and back to find out that everything is fine. I think it may be the test.