Crossroads - S1-E5
Revealing mistake: When Easy is paddling across the river to aid the British soldiers, there is a shot where the person closest to the camera (Bull Randleman) appears to be rowing, but there is nothing in his hands.
Revealing mistake: When the first tank comes during the final battle, look carefully at the German sitting on it and you will see that he's actually a dummy.
Revealing mistake: In "The Breaking Point," Lipton is narrating the bombardment of the woods right outside of Foy. Just before he says, "What I saw that day," at 30:55, you see a section of a tree explode, but when the debris (i.e. the splinters of wood and snow) clears you see that the "blown up" section of the tree is unharmed. (00:30:55)
Day of Days - S1-E2
Revealing mistake: When we see the German getting shot in the trench at the 88 station, a blood squib pack can be seen on his right-hand chest pocket before it goes off. (00:31:20)
Day of Days - S1-E2
Revealing mistake: During the battle to take out the 88s, the camera pans to Lt. Winters reloading his M1 Garand. If you look closely, you can see he is loading blanks into his weapon. (00:31:29)
Revealing mistake: When trying to take the warehouse, we see a German machine gun position in a lower window. Pay close attention to the brickwork below the window. There are several marks visible that all end up with a bullet hole in the middle of them, hiding the charge for the effect. (00:14:30)
Replacements - S1-E4
Revealing mistake: Just as the one soldier is sent flying over the wooden fence surrounding a building, you can see break away marks on the post where he will hit it. (00:34:40)
Replacements - S1-E4
Revealing mistake: Just as the Tiger fires its second shot and hits the garage, look closely and you can see where the break in the wall is going to appear. (00:32:05)
Day of Days - S1-E2
Revealing mistake: When placing the German grenade into the barrel of the German, gun you can see the cord used to set timer is still attached. (00:36:40)
Suggested correction: The cord doesn't have to be fully removed for it to work so showing it like that is not a mistake. The grenade will smoke quite a bit if the primer is ignited so even if the cord isn't fully removed they'll know quickly enough the pull was hard enough to ignite it.