Then there were the subtle forms of sabotage. The Nazis were focused on the use of slave labor, missing the fact that it would be easy to do hidden damage. From a book by John Diebold, Chief Scientist for Marine Operations in Norway
In 1978 I worked with Norwegian colleagues during a US–Norwegian geophysical study of the Norwegian continental margin. For seismic sources, we used World War II surplus Nazi explosives which were stored in man-made caverns along Norwegian fjords.
It was my personal observation that while the munitions dated 1939–1940 were reliable, those with dates from 1943 and later were typically weak or noneffective. This difference I ascribe either to intentional sabotage by the “Jews and concentration camp inmates” or to the simple substitution of inert materials for active ones by munitions plant managers, presumably due to the conflict between production quotas and availability of nitrates.
Speer was apparently not above “production for production’s sake” with a blind eye to quality control.
Then there was this incident reported by Richard J. Evans.
A German bomb fell through the roof of my wife’s grandmother’s house in the East End of London in 1943 and lodged, unexploded, in her bedroom wardrobe. When the bomb disposal unit opened it up, they found a note inside. “Don’t worry, English,” it said, “we’re with you. Polish workers.”
This is resistance. This is courage.