The PT6 has a mean time between failures of less than 1 failure for every 100,000 hrs flown. If you have had 2 failures of this type of engine than my thought is the engines were not properly maintained. An engine failure because the engine is not properly looked after IMO falls into the preventable enginr failure catagory.
Once again we have statistics that only point out an average.
Both of my engine failures on the PT6's had nothing to do with not being properly looked after.
Here again is why they failed.
Two were fuel controller failures on PT6's.
The engines were PT6-20's.
The company I was flying for had a lot of these engines in their Twin Otters and their Turbine Goose's.
Mind you that was some years ago though and it is possible you were not flying for a living then so you may not be familiar with the problems we had with fuel controllers then, in those engines.