The one example that I can think of is the Battle for Castle Itter.
Castle Itter was an Austrian castle used by the Nazis as a prison for French VIP prisoners. As the end of the war neared, the guards fled and the prisoners armed themselves and sought help. A small group of Wehrmacht soldiers who were looking to surrender agreed to protect them from Waffen-SS in the area. They were later joined by a small American unit. Shortly thereafter they were attacked by Waffen-SS units who may have been intending to execute the French. The Wehrmacht troops, former French prisoners and American troops fought side by side to defend the castle, holding out until American reinforcements arrived.