Well, mine doesn't seem to have the rattling arm issue either, I feel as though even if it did rattle, it wouldn't be an issue because I have always used an external Microphone. As well as a shoe mounted flash not the internal flash. And in cases where I've used the internal flash its been for i-ttl which also isn't an issue. Seems this random issue doesn't affect everyone. But its also not so big of an issue either.
This is my attempt to soak up knowledge like a sponge..