A German penal battalion (construction troops, I believe) defended the small town of Kurkino (north of Spas-Demensk) on 17 March 1943. Kurkino lies within German 4th Army boundaries, although I don't know if they were subordinated this army. I assume they were primarly there to construct a segment of the Buffalo line. They are referred to as a "Bewährungsbataillon" in my source, and are (or at least includes) Wehrmacht troops who have committed some sort of minor felony.
Does anyone know which penal unit this might have been?