The Thielerts are, or at least used to be, horrendously unreliable. My good friend manages a club/flight school with quite a few of them, and they have been nothing but trouble. They lost 2 172's already, one for clutch failure, one for a fuel pump failure, and the turnaround time for overhauls is over a year currently.
The Austro doesn't seem much better with constant fadec problems. One of their 172's with is has been grounded for close to a year for lack of parts.
These are high utilization planes though but these engines are clearly not suited for that.