That's a bummer to hear, I know that pain. I blew through 2 shutters on my first 645D, got them both replaced under warranty. (Though it was a fight both times, and took a staggering amount of turn-around time with the main repair centre in Japan.) Ricoh/Pentax did redesign the shutter for the 645Z, thankfully, although that doesn't help anyone if it eventually does fail.
My Z was the first or second one in Western Canada, I think. I've shot the hell out of it and it has been a rock. (Save for multiple failures of the cable remote socket, which I eventually just stopped repairing.) I'm somewhere around 100K shutter actuations, a bit hard to tell because the service centre reset the count at least once, maybe twice. But I reckon it's still just a matter of time before I'm replacing my Z shutter too...
