After Saunders and Caje free the truck from the mud, they come across the mother and son dragging the heavy casket, which was lighter earlier, and it now has a lid, but it had no lid earlier. They put the mother, son and the casket in the back of the truck. When Saunders takes the casket out of the truck to support the bridge, the lid is gone.
As Caje is guiding Saunders and the truck across the bridge, a close-up view of a tire is shown, along with the shadow of a hand holding a cigarette. Caje wasn't smoking. This might have been a director or other crew member that got too close to the camera's view.
After the truck got stuck in the mud, the woman and her son are seen dragging what appears to be a heavy casket with a lid on it. Earlier, there was no lid, and the casket was light enough to slide around in the back of the truck.
When Sanders takes the gas can from the German truck there's still a gas can on the side of the truck even when the Germans take off in the truck there's a can there. When the Germans find the gas can that fell out of the old women's truck there is no gas can on the side of their truck. There
isn't even a bracket to hold the cans.