It sounds like something between the inner lining of the drum and the outside casing (if that's how it's made up). When I say the front is off, I mean the front of the machine and not the front bit of the drum, so I can't see inside - if that makes sense. It's definitely not a bra wire. Just wondering what the bang could have been.
Stupidly, I didn't stand over him while he was looking inside as was busy doing some work.