Plot hole: There is no reason at all why, being targeted by a few arrows by unseen enemies - a fire suppressed already by the salvo of their own archers - the Rourans would turn around their heavy siege equipment, away from the bulk of the enemy forces, and fire it, hurling a single heavy stone to the middle of nowhere when they have the whole rest of the army who could storm the rock the supposed enemy commandos hide behind, or the archers who could keep shooting - again, they proved to be completely successful. It also makes no sense that the all-powerful witch who made the warriors flee managed to do any of this, 'sneaking' by horse in the middle of the steppe.
Plot hole: The 'avalanche scene' in this remake is mind-boggling. For starters, the Witch single-handedly holds the whole Chinese army at bay splitting in a zillion of flying creatures - a power level completely inconsistent with the rest of the movie. To the annoyance of being pounced by little birds, the army gets in turtle formation, apparently just waiting it out. The Rourans somehow are ready for this and have a trebuchet set up - despite the fact that they are nomads, conquered the forts infiltrating them, and they were skirmishing a moment before. They throw flaming boulders with such precision that they are able to target each single 'testudo', multiple times, with the soldiers just sitting there with no reaction.To save them, Mulan is able to sneak behind them UNSEEN, by horse, with a bunch of extra helmets she somehow carried, set them in place, and fool them. Any of these convoluted operations would have taken an impossibly long time.
Continuity mistake: After Mulan breaks the winged sculpture she chases the chicken and runs past a couple. A mere second later Mulan is in a different place: the stuff on the wall has vanished, the ladder and, of course, the couple. There's a brief shot afterwards where you can now see the ladder but the couple is nowhere to be seen. The whole editing is a mess.
Continuity mistake: Mulan opens her armor to extract the throwing weapon blocked by her makeshift corset. In the first close-up the long strand of hair that was in front of her left hand is gone, and in the second one (when she pulls the weapon out) her left hand is holding the armor below the dagger - it was above it before. (01:04:25)
Continuity mistake: After the first clash with the Witch, as the narration says Hua Jun 'dies', but Mulan lives. The close-up on the blade shows a hand gripping it a couple inches below the blade, while whenever we see her face, before and after that close-up, she is holding it with her finger alongside the guard. (01:03:45)
Continuity mistake: Once Mulan has reached the top of the mountain with her buckets, the action moves to the Rouran troops assaulting a city. Gong Li's witch is womanhandling a bunch of soldiers who try to impale her. She grabs a spear a few inches away from its feathers, but in the next shots her hand is covered by them. (00:50:50)
Continuity mistake: The commanding officer (Donnie Yen) intervenes to stop the sword-pointing nonsense with his kung-fu badassery. He easily disarms the two litigious rookies and holds both their swords, but the pose he strikes is a different one in the two shots; Mulan's family heirloom is held alternatively low and high. (00:29:55)