In the last 10 minutes of the movie, a character is shot by several other characters.
With each of these shots, an empty shell casing should have been ejected from the rifles (M1 carbine and M1). In addition, the empty brass would have made a noticeable "tink" sound as it hit the stone floor in the cellar.
When the "German" tank attacks the "V" shaped main gun support (used only when moving long distances and never in combat) is clearly visible. A few seconds later the support is missing. A second later it is back in place.