Continuity mistake: During the throne room fight against the red-armoured guards, one of them splits his weapon into 2 blades. In the shot where he gets Rey into an arm lock, the blade in the guard's left hand vanishes from the scene completely, in the middle of a shot. The hand that held the weapon is obscured by Rey's body at the point when the disappearance happens. It could be that the actor dropped it (a strange thing for an elite fighter to do), but then the blade is nowhere to be seen on the floor in the wider shot when Rey kills him.
Continuity mistake: As Poe Dameron starts his attack run against the Dreadnought we initially see him from the side and his helmet microphone is folded out to the left away from his face. The camera cuts to directly in front of Poe and the microphone is now folded in and directly in front of his mouth. (00:03:25)
Continuity mistake: When Poe realises that Holdo is fuelling up the transports, he is suddenly much closer to her than he was in the rest of the scene.
Continuity mistake: When Rey is following Luke upwards the steep terrain, between the two shots in which Luke is visible, there is a shot of Rey kneeling down, following up with her noticing the old Jedi tree. Given the amount of time the camera was focused on Rey, Luke should have been significantly further away as of the second shot in which he is visible. Instead he is seen continuing walking, starting from a point that he had already passed in the previous shot. (There is one dark spot on the ground, in which Luke can be seen walking past to his right in the first shot, which can be used to help identifying the mistake). (00:21:40)