Sorry if this is outside of the scope of r/AskHistorians but 13 years ago my family had some of my Oma's memories of her life in Germany.
According to my Oma, her parents hated Hitler and their village's Bauernführer. My great-grandfather was a World War I veteran and had rheumatism, so according to my Oma, he should have been exempt from the war, but apparently due to their dislike of Bauernführer and the Nazis he was conscripted in 1943 at age 51. When he came back a month or two after the end of the war, they found out he was guard in a concentration camp and apparently he had secretly let some prisoners escape when he knew the war was lost. According to my Oma, her mother never found out what her husband did during the war.
Given my Oma's age and how long it was before these details were recorded, I don't know how accurate these details are or how plausible the events were. Were people conscripted as retribution? Were conscripts sent to be guards in concentration camps? Did guards ever secretly let prisoners escape?
/u/warneagle has previously answered Were guards for Nazi Concentration/Extermination camps specially picked, or just assigned there?
/u/vonadler has previously written about non-Germans in occupied countries being conscripted to serve in the military, with the caveat that who "counted" as German was sometimes arbitrary.
/u/kieslowskifan has previously written about the competing recruitment needs of the German military and the SS.
See below