Continuity mistake: As Rey tells BB-8 that he can stay with her, you see the droid behind her from a frontal view. When it cuts to a side angle of BB-8, the lines and details on the side of it's head close to it's "eye" change with more lines appearing, the orange rectangles at the bottom become taller, and the white rectangle box moves higher up. Also in the side view there is some black cone sticking out of what would be BB-8's "face." If it's his eye it's now suddenly sticking out way too far and isn't that extended. If it's the little censor thing that is next to his eye then it's now on the wrong side of his head. (00:00:25)
Continuity mistake: When BB-8 hears the creature come up from the sand behind him, he stops. Just before he turns around the orange rectangles on the left side of his face to being almost all uniform in shape and size, to now having two big ones on the ends and two small ones in the middle. (00:00:30)
Continuity mistake: The nightwatcher worm comes up out of the sand right next to BB-8's trail through the sand. After Rey identifies it and the creature is about to duck down under the sand, the trail BB-8 left behind has vanished. (00:00:45)
Continuity mistake: As Rey is retrieving her staff with a slimed BB-8 in her grasp, she passes by and leaps onto the leg of an old fallen AT-AT Walker which is next to her. There is a fin sticking up into the air from its foot with a groove down the middle in the close shot as she gets her staff. In one of the following shots as she's jumping up onto the leg, that middle groove on the fin disappears. Also in these shots, suddenly much more sand is built up against the foot of the Walker than before. (00:02:00)
Continuity mistake: Rey grabs BB-8 and her staff, and then jumps up onto a fallen AT-AT Walker. She turns to look at the Nightwatcher worm and is standing right next to a very slime covered BB-8 on top of the AT-AT with her hand on his head. It cuts to a shot of the Nightwatcher from over Rey's shoulder and then back to a frontal view of her again from a higher angle. Rey didn't move once during those shots. But now she's suddenly standing further away from BB-8 to show the junk part between them, BB-8 now has much less slime on him, and the groove in the metal of the walker going down vertically behind BB-8 has vanished. (00:02:05)
Continuity mistake: The piece of junk that Rey feeds to the Nightwatcher worm appears between her and BB-8 with the pointed end of it facing away from BB-8 towards Rey, with the round end pointed out. When she bends down to pick the junk up, in the close up the pointed end is now facing outwards from between her and the droid with the round end towards BB-8. (00:02:10)
Continuity mistake: BB-8 and Rey watch the Nightwatcher Worm go away after she feeds it and you can see BB-8 with the slime on him. It cuts to a different angle just before the droid asks her how she found him, and the slime spots on the side of his head change shape and size.Most notably the middle spot shrinks significantly and the bottom one over laps the edge of his head. (00:02:25)
Other mistake: Never once does Rey leave any footprints in the sand, despite her being heavier than BB-8. And BB-8 leaves constant trails in the sand wherever he goes.