The September 4th case where a German officer called in American air support which killed an unknown number of people in Afghanistan - anywhere between 17-142 of them - has been investigated by NATO and the officer was found to have acted reasonably. Perhaps not perfectly, but that's war. The case now goes to the prosecutor in Dresden, who will decide if there's justification for criminal proceedings.
Most of the German media accepts the results; one left-leaning paper is very cynical about it. Der Spiegel has the roundup.
I don't see anyone calling for "independent external investigators", but maybe I didn't look carefully enough.