deice
It's only a mystery until the engine stops. Then the mist clears slightly.
PT6s do go bang. I have flown passengers on a route that was usually serviced by an aircraft that shredded one - including pax who were on the aircraft when it happened. They were glad of the second engine!
There have been potential replacement modern twin pistons, including diesels (TT62 for example). Unfortunately those I know of have not succeeded. The current core of the market relies on second-hand airframes, due to the cost of purchase of new aircraft. The implications for the future of a poor market for new PA-31-sized twins are an increase in cost in the light charter market in the next 10 years.