When Sarah enters her house just before Michael is leaving for France, all the windows are broken. From the inside they suddenly are fixed again.
The position of the German's bayonet over Dunne's chest during the scuffle.
During one of the close-ups between Dunne and Mann, the rain has stopped. In the next scene, it is once again pouring.
In the climactic battle sequence (1:33'51'' mark) as a German soldier stabs a fallen body, the bayonet bends as if made of rubber.