According to the German newspaper TAZ, judges in the Thuringia district of Gera share close ties with AfD politicians, both locally and nationally, quoting statistics of judges deciding in favour of asylum seekers in single-digit percentages. The judges have denied having any right-wing-leaning biases.
It is, alas, basically impossible to nail judges for perversion of justice based on statistics because you have to prove at least reckless intent. Add to that judicial independence and the possibility to do anything are very limited, I think at most stuff like re-distributing judges among districts to even out statistics would be constitutionally viable. Giving a general directive to state attorneys to appeal sentences which seem too harsh or lenient is also an idea, and push come to shove those appeals could be done by a special task force.