I suspect there is a lot more going on with the Thielert engines than we read about publicly. I know a few owners personally (face to face) and their stories are pretty amazing.
It's not in the interest of somebody with problems to go public; if they do they get cut off from support by the dealer/manufacturer. I know this from personal experience. Once out of warranty, this changes and people do speak out, but this has not been the situation here because Diamond/Thielert have been doing various "deals" to keep people hanging in there. Anyway, you don't exactly have any other options, other than to send the whole plane back for a refund (and yes that's been done too).