Operation of the engines beyond recommended overhaul period WITHOUT the benefit of mandatory accessory (think fuel pump, fuel control, prop governor) replacement and enhanced engine condition (Oil analysis AND vibration analysis) monitoring that is required by approved service life extension programs. The PT 6 will usually talk to you for a while before it fails. Perhaps skydive operators aren't listening.
My resume; A&P, I.A. ATP King Air Charter and skydive pilot 34 years in civilian aviation maintenance and flight operations.