Other mistake: The character Su-mi is depicted as an adolescent girl in her teens. She is introduced in Episode 2, which is set in 1902. Episodes 2 through 22 take place between 1902 and 1904, then a 3-year time jump occurs, meaning Episodes 22 through 24 take place in 1907. Also, the final time we see her, she is shown as a member of the Righteous Army which takes place two years after 1907 (1909). Yet during this 7-year timespan, she shows no signs of ageing.
Episode #1.3 - S1-E3
Other mistake: Dong-mae is standing atop a balcony, several meters above ground. Yet he is able to fully hear a conversation that two men are having about Ae-sin whilst they are on the ground and standing far away from the building he is in, without any of the other people or market stalls drowning out the sound. (00:16:59)
Episode #1.5 - S1-E5
Other mistake: When the women are practicing their archery skills, one of the women says "I wonder why Lady Yun is absent today." But the captions add an extra N to the name Yun, misspelling the name as Lady Yunn. (00:15:41)
Episode #1.7 - S1-E7
Other mistake: When Tsuda and Yamada are in Hayashi's office, Hayashi takes out a sword and executes Yamada. Based on the length of the sword, and the distance between where Hayashi was standing and where Yamada was kneeling, there is no way the sword could have killed Yamada. Tsuda was in between the two and the sword wouldn't have been long enough to reach Yamada given how far apart he and Hayahshi were. (00:17:10)
Episode #1.9 - S1-E9
Other mistake: The blood stain on Se-hun's collar shown when Eugene slices his neck doesn't seem possible. Within just two seconds of the side of his neck being slit, his collar appears to have been covered in blood, indicating that he must be bleeding at an incredibly fast rate, but for the rest of the scene, his neck never continues to bleed. (00:56:03)
Other mistake: Chun-sik is standing next to a sweet stand talking with the vendor. Whilst he is saying "You know, I was quite skilled with swords back in my days", he is shown holding some bread, but he is not shown eating it nor is he shown taking a bite. The vendor then starts saying talking and Chun-sik still does not eat any of the bread, but then he is suddenly shown chewing, even though he never took a bite out of the bread. (00:07:15)
Other mistake: Dong-mae grabs a sword and slits the throat of a Japanese man, which causes blood to get splattered over both the left and right side of his face, as well as his neck and his chest. This would not be possible for multiple reasons. One, the slit was relatively small, so there wouldn't have been that much blood. Two, Dong-mae was standing too far away from him for the blood to travel that far. Three, Dong-mae had his head turned away from the man when he slit his throat. (00:43:19)
Other mistake: When Mr. Haengrang is lying on the ground after being shot, there are tiny drops of blood visible on his face, presumably blood splatter after getting shot. However, when he was shot just seconds earlier, all the gunshot wounds he received remained inside his clothing and there was no blood splatter of any kind shown, so there is no way any blood could have splattered on his face. (01:18:30)
Other mistake: After Haengrang and Haman have succumbed to their wounds and died, a puddle of blood can be seen in between the two of them. The problem is, this puddle of blood doesn't appear to be emerging from anywhere. The blood shown on the ground would have come from their wounds (and would have formed the puddle of blood), but the puddle isn't connected to either of their bodies. (01:19:40)
