When Valiant is shown standing after picking up Merlin's goblet, it is yellow in his hand rather than clear.
Before the dream sequence where Arthur appears to Merlin at the window, the hourglass is shown three-quarters empty. But in the next shot of it after the dream, it is only slightly more than half-full.
When Om approaches Valiant, next to the others, with the potion, he walks over to him and the end of the shot shows him extremely close, where he could only take one more step before running into him. But in the next shot Valiant has moved forward so the others are behind, but Om still has a few steps to go to get to him.
During Arn's rapid ride and the following fight in the woods, none of the horses leave hoof-prints in the snow.