Yes, one case that comes immediately to mind is Max Taubner.
Prosecuted bec ause of excessive cruelty and also taking unauthrorized pictures of atrocities, and sharing them with civilians at home. In other words, war crimes even in the mind of the SS, and potentailly letting the cat out of the bag as to war crimes.
Oddly, he was convicted and punished but later pardoned and reinstated by Himmler himself due to war need. After the war, the new German government wanted to prosecute him for his very real war crimes but found that since he’d been tried, convicted, and punished already, prosecuting him post-war would constitute double jeopardy, and so the case was dropped.
The Nazis were signatories to most of the Geneva conventions, and as far as actual acts of war went, they did a better job of eschewing War Crimes than the Imperial Japanese or even the Soviets. However, they did not seem to have much in the war of a concept of “Crimes against Humanity” under which the Holocaust would be classified. The Nazis seemed to think that the thin veneer of legality in which they draped many of the atrocities made them somehow legal.
So yes, the Nazis were fairly up on War Crimes, but not so good on “Crimes against Humanity”, since as Dissonance pointed out, there were no such “crimes’ at the time the Nazis committed them. As Quincy Wright sez “ How can principles enunciated by the Nuremberg Tribunal, to take it as an example, be of legal value until most of the states have agreed to a tribunal with jurisdiction to enforce those principles? How could the Nuremberg Tribunal have obtained jurisdiction to find Germany guilty of aggression, when Germany had not consented to the Tribunal? How could the law, first explicitly accepted in the Nuremberg Charter of 1945, have bound the defendants in the trial when they committed the acts for which they were indicted years earlier?”
In fact some of the sentences, such as against Karl Dönitz, were mostly political, as the Admiral tried as hard as he could to keep within international law as he knew it. The charges against Raeder were similar political. Several high ranking Nazis were convicted of “conspiracy to commit aggression against Poland in 1939” but the Soviets got a pass on their identical crimes.