When the gun is being moved across the old bridge, some wood breaks and a wheel drops down through it. The position of the wheel changes when the camera angle changes.
After they knock out the German A/T gun, Wayne Rogers looks at the gun and says "Hey look at this. They really make them beautiful, don't they?" Trouble is, the gun is really a British 25 Lbs. or its American equivalent 57mm anti-tank gun.
When Sgt. Hagen is in the turret of his tank, talking to Sgt. Saunders, he is wearing a standard issue M-1 helmet issued to most troops. US tank crews wore M-1938 tanker helmets which contained headphones and a microphone. This allowed them to talk to each inside the tank as it was quite noisy. The crew may have carried M-1 helmets in stowage boxes for use when not in their vehicle, but when in their tank they would wear the M-1938 and not an M-1.
When the Germans destroy the American tank and half-track, some of the Americans run and jump over and hide behind some fallen tree trunks. They are obviously fake, as they wobble too much.
The American tank used is an M-41 Walker Bulldog. They were built from 1951 to 1954 long after World War 2 was over.
Saunders calls Wayne Rogers character by his real name "Rogers" not by the character name of Reiser.
After the gun battle when the GI's kill all the Germans, one dead German is shown twice and he is moving.
In the quick firefight after the horse gets away from the gun it is pulling, the Americans walk past the German bodies. One of them is still breathing, but appears to take a little breath and hold it.
The last hill they have to go up with the gun is the longest and steepest. There were a couple crates of ammunition on the cart, plus other tools and equipment. If they unloaded the crates and carried them up, and just discarded the tools, it would have made a difference in getting the gun itself pulled up the hill.
When the German squad following them is killed, the dead German sergeant is seen to move, twice.