Certainly Sabotage was committed as one form of resistance, even if historical documnets don't mention it. The Saboteurs, as can be understood easily, weren't eager to leave proof of their deeds. Opern resistance took place as a strike in an External Det. at Hamburg with the aim of improving the work conditions, in which it did succeed. At the Sandbostel Camp, French NCOs refused to work, because according to the Geneva Convention, they were only allowed supervisory duties. And Italian officers did resist to recruitment offers of the German Wehrmacht.
Since April 1944, the resistance movement in the Camp owned a short-wave radio-receiver and -sender for listening to BBC war reports and relaying theese to other groups. So the different groups of POWs in Germany were quite well

informed about the war Situation. The separate French groups did unite themselves to some sort of Underground army, nearly 1200 strong.
When Germany's defeat and the Camp's liberation could be seen to emerge, the prisoners prepared action plans for the following possibilities: evacuation of the inmates, flight of the guards, fight for the Camp. Depots for weapons and ammunition were investigated, maps drawn and gathering of intelligence stepped up. Many informations about war criminals and high-ranking nazis were collected. Unfortunately, these, like many other documents, became lost. Immediately before the war's end, control of the Camp did pass to the POWs, who cared as best as possible for the KZ prisoners. After liberation, the British Army took over command.