At the beginning while down in the tunnel, Carter's helmet has an insignia on the side. But when they come up from tree trunk, the insignia is gone for the rest of the scenes. Update: The insignia reappears on the helmet when Carter puts the uniform in the table after the roll call, but is missing again when he comes back to camp on the motorcycle.
When Colonel Klink is talking with Colonel Hogan in his office, the amount of wine in Colonel Klink's glass changes. Update: Specifically, when Hogan is in Klink's office, trying to convince Klink to discontinue the new nightly roll calls, Hogan says, "You know, frankly, I - I think you should discontinue the roll calls, sir." While he says that, he walks behind Klink, over to the room heater. After that, the level of wine in Klink's glass has increased substantially. Note that, at the same time, the quantity and arrangement of food on Klink's plate changes as well.
After planting the dynamite, Carter says, "The charge is all wired. All you have to do is hit one and they all go off." The problem is that the detonators they were using were electrical, and would require an electric charge to fire the detonators. Hitting one of the dynamite charges would not generate an electrical charge in the wiring, so it couldn't fire the detonators.
The patrol leader that catches Carter was marked as a private. As a patrol leader, he should have been at least a gefreiter (lance corporal), with one or possibly two chevrons on the sleeve.
When Carter comes into camp in the motorcycle sidecar, there is already a track of a motorcycle on the ground, indicating this is a second take of the arrival.
As in Hogan Goes Hollywood (1969), when the bridge explodes, it is apparent that the train tracks end at the front edge of the bridge.
During the introduction, as Carter carries the detonator box up the ladder and out of the tunnel, he swings it around as if it is empty (which it probably is). The box, if real, would have a mechanical generator inside (similar to an alternator in an automobile), which is a fairly heavy object. For comparison, the alternator for a 2007 Audi A4 weighs just under 15 pounds (approximately 6.75 kilograms). Generators from 65 years earlier would almost certainly have been heavier.
When Hogan is in Klink's office, trying to convince Klink to discontinue the new nightly roll calls, Hogan says, "You know, frankly, I - I think you should discontinue the roll calls, sir." While he says that, he walks behind Klink, over to the room heater. While he walks around Klink, the camera shift to keep both characters in view. During the shift, the shadow of the camera crosses the table.
At the very end, Klink says, "A man like that - hmf - you just never know." At that time, he looks slightly upward, and a full reflection of the stage light can be seen in his monocle.
During the introduction, when Carter carries the detonator box up the ladder and out of the tunnel, he swings it around as if the box is empty (which it probably is). He should have made some effort to act as if it was heavy enough to contain a generator to generate the detonation pulse.