So the owner was on a road trip from Sydney and had just had the bike serviced. He'd noticed a clicking noise at low speeds so took a closer look
He sent a picture to the dealer in Sydney saying he'd get a spanner to tihghten the nuts. And was instantly told "Do not tighten those nuts, whatever you do"
Turns out, as Greg suggests, the threaded studs are unscrewing out of the wheel hubs.. A mechanic tried tightening the studs and failed, and Sydney then said words to the effect of "replace the hub in melbourne or you will die". Indy mechanic in Melbourne pulled the back wheel and said the wheel bearing was a mess, chain a mess, seals are a mess, as well as needing the new hub and sprocket.
But he's having visions of the sprocket breaking free at speed on the road so is thinking himself very lucky, if not poorer