Visible crew/equipment: At the surrender of the fort, as the English are marching out, the French general removers his hat. The English Commander, Monroe, says "The fort is yours, Monsieur". Look over his shoulder. In the distant valley you can see what are either two tourist busses or perhaps mobile catering vans.
Revealing mistake: Near the very end of the movie, when Magua has taken Uncas' love interest (Madeleine Stowe's character's sister) and he is taking a path through the mountain, Daniel Day-Lewis runs up a path and brushes against what seems to be a rock. But, the grey coloured "rock" seems to be a prop and moves like a piece of cloth.