Continuity mistake: In the scene after the battle at Petersburg, Inman is guiding his wounded young friend out of the crater back to their camp. Next to the road to the camp you see several big piles of dead Union soldiers, probably to show how bad the battle turned out for them. But wouldn't it be logical if the Confederate soldiers first saved their own wounded soldiers, and only then arranged the bodies of their dead enemies? Inman was very concerned about his young friend and was still in good state after the battle, surely he would have gotten him out a lot earlier after the battle.
Continuity mistake: We see Oakley on a stretcher after the battle in the crater and he is talking to Inman, and then we see him in a tent (before he dies) asking Mr. Thewes to play him "something sweet". In these two scenes, the blood and mud on Oakley changes entirely. There is no reason it should change in such a short interval.