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.James Rice
Continuity mistake: During Kylo Ren and Rey's fight against the guards, he drops his lightsaber and needs Rey's to finish off the fight. After they force fight over her saber they're knocked out. When Kylo comes to, his saber is back in his belt.
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 Rey is practising with the lightsaber on Ahch-To, she swings it very close to a towering rock. The camera then cuts to a wide shot showing her with the lightsaber, now feet away from the rock she was only inches away from in the prior shot.
Continuity mistake: When the light saber breaks in half, Ben is thrown to the left of the throne while Rey is thrown to the right. Once Ben wakes up, he is on the right of the throne, exactly where Rey was when she refused him. (01:51:50 - 01:55:10)