Plot hole: At the beginning of the movie it is said explicitly by the Chancellor that the Rourans have attacked 6 garrisons at once, disrupting trade on the Silk Road, which would, in his words, threaten the survival of the whole Empire. It's a bit odd considering that their assault relies on the Witch's abilities, and she can't be everywhere at the same time, but forgetting that; the Emperor to counter this urgent menace (Bori Khan slaughters everyone in the cities) decides to summon to arms literally the whole kingdom amassing a huge army. This obviously is a project that takes months (we even see Mulan taking days just to get to the training spot, and then they train long enough to become proficient in archery when they started off not able to even throw an arrow) and does absolutely nothing to stop the brutal raiding and killing, but somehow Bori Khan's plan is kindly waiting on Mulan and her buddies to train, despite being a plan based on speed, surprise and distraction.
Suggested correction: First, it is not fair to cram so many "mistakes" into one entry. Second, it is your personal assumption that all six attacks relied on the witch. Third, she can transform into a bird and fly; certainly, she can catch up with multiple attack forces if needed. Fourth, it was an empire, not a kingdom; a super-massive empire called China. Fifth, training a relief force is also part of the call to arms. Where there is a battle, there is death. Dead units need to be replaced. Sixth, "speed" didn't come into play in the strategic aspects of warfare until World War II. At the time of this film, they were tactical elements. Wars went on for years, sometimes decades. China was a huge empire and conquering it quickly is impossible. Seventh, you've already explained the reason behind Rourans' delay into another mistake entry you posted: They were carrying catapults and they had practiced using them.
Entry is articulate because they are not separate mistakes, it's just that the "strategy" employed by the invading army and the response to it is all over the place and contradictory (1). They show and say in every possible way that the reason garrisons fall so quickly is because of the witch intervention and they depend on her (2). Catapults are never shown as being used for city assault (7), and it's obvious why; walls are bypassed, cities don't take months and huge armies to be taken, they fall in minutes (6). The climax of the movie itself happens with the invading army crushed, the Emperor knowing it, but their plan is perfectly successful, since they made it through the super-massive kingdom from the Silk Road battle, without being able to fly, simply outmaneuvering everyone with a tiny group of jedis (3-4-6 again). See original entry for why 5 is absurd;anything else I mentioned was not flavour or additional mistakes, but just context.
Continuity mistake: When Mulan baths in the river and his friend enters the water, a strand of hair along her left jaw appears and disappears randomly.
Audio problem: During the avalanche, Mulan's horse makes the exact same sound when galloping on dry hard ground and when he gallops on soft snow.
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: After jumping off the roof, Mulan smiles at her dad while neighbours walk away, and a strand of hair falls over her forehead. A shot later her hair is brushed. She didn't move between shots.
Continuity mistake: In the desert, when a man sees Xianniang he wipes is face with a handkerchief. The way he holds it changes between shots.
