PW's were not allowed to wear their uniforms except at funerals. The SS officer would not have been wearing his SS uniform and certainly not a Swastika since political emblems were not allowed.
Auto pictured late in movie is a 1947 Hudson Hornet. The movie setting is 1944-1945.
The front gate at Camp McCoy was two field artillery pieces framed in stone gateway sections. Not a wooden shack.
It was the rule that captured SS officers were kept segregated from regular German army troops and were guarded more closely.
When the German boy puts the egg nest back in the tree, you can see one of the eggs drop as he is climbing down the tree.
The shirt and collar worn by the priest is a design that wasn't available until the late 1960s.
Near the beginning of the film, when the bus is going from Wisconsin to Chicago, huge mountains are seen in the background. There are no mountains in Wisconsin.