Continuity mistake: During the escape from Jakku, the Millennium Falcon is battling two tie fighters and Finn's cannon gets stuck in the forward position. After Finn shoots down the 2nd tie fighter, he is shown celebrating. In the shot, Finn's cannon is no longer stuck in the forward position and is now pointing up. (00:35:35)
Continuity mistake: When the imperial officer is informing Kylo Ren that they were unable to find the droid, Kylo slowly turns his head around. In the next shot, from far away, red lighting has appeared on the left side of his mask. The shot cuts back to him and the red lighting on his mask has vanished. (00:36:50)
Continuity mistake: After BB-8 tells Rey that the Resistance base is located in the Illenium system, while Rey is down in the hold she asks Finn for something she needs and she holds her right arm up and points, but in the shot facing Finn it's her left arm that's up pointing as she repeatedly shouts "NO!" to him, and then it's her right arm up again. (00:38:40)
Continuity mistake: While Rey's fixing the motivator, when Finn asks her if she wants to go back to Jakku because of family or a cute boyfriend, Finn's kneeling on his hands and knees, but in the next shot he's not, just as Rey tells him it's none of his business. (00:39:00)
Continuity mistake: When the falcon is caught in the tractor beam, in the shot after Finn says "it's the First Order," the shot cuts to Rey saying "What do we do? There must be something." There is a strand of hair on the right side of her head, and as the shot ends, the tip of the strand is pointing away downwards. In the next shot, the tip of the strand is suddenly curled up and closer to her neck. (00:39:35)
Continuity mistake: When Finn asks Rey if she can unfix the poisonous gas they rush to get the air masks, and as Finn climbs down to the maintenance bay below deck we see the floor behind Rey when she starts to kneel to help BB-8. Then after the closeup of Rey helping BB-8, in the next shot as Finn takes BB-8 from Rey we see the corner of the floor's deck plate that has suddenly appeared behind Rey, which she reaches for in the following shot to cover the maintenance bay. (00:39:45)
Continuity mistake: While Finn, Rey, and BB-8 are hiding in the maintenance bay to unfix the poisonous gas, when Finn lifts the floor's slotted deck plate and pokes his head out there are specific grooves at the edge on top of the plate, but no grooves underneath at the edge. The problem occurs when Chewie lifts the deck plate, and those grooves should be on the side facing him (the top side), but instead they're facing out. Then when Han tells Finn "that thing" can understand him, the grooves are gone - the top side of the deck plate is properly facing out. (00:40:05)
Continuity mistake: When the members of the Kanjiklub arrive on Han's ship, the airlock opens, showing two members standing ahead of three others, with a gap between the two in front. The shot cuts to a closer shot and the distance between the two has decreased. (00:44:35)
Continuity mistake: When the rathtars begin attacking, in a shot of Han looking down the corridor, one of the Kanjiklub members is running through a doorway whilst running from the rathtar. The camera cuts to a closer shot of them running from the rathtar, and the same Kanjiklub member can be seen running through the doorway a second time. (00:46:00)
Continuity mistake: When Rey fixes the Falcon's electrical overload she pulls out blue and red wires, but just as she says, "I bypassed the compressor," in this shot facing her there are only four blue wires - no red, and then the red wires reappear with the blue. (00:51:55)
Continuity mistake: During the exchange between Ray and Solo note the compressor she is holding. The wires are at the top, next shot these are at the bottom, then they are back at the top, and in the last shot the wires are gone. (00:51:55)
Continuity mistake: After the spy, Bazine, communicates that she's found the droid at Maz Kanata's, in the following side closeup of Kylo Ren we have a good view of the distinctive surface dents/hole on the side of his mask (his left side) and this is a flipped shot, then in the front closeup of Ren those dents/hole are now on the opposite side of his mask with different marks the other side. (00:58:55)
Continuity mistake: When the general is giving his Starkiller speech, there is a Stormtrooper is on the far left of the screen with a red shoulder pad which is down. It is fixed later in the sequence. (01:08:40 - 01:09:15)
Continuity mistake: After the Starkiller Base weapon is fired at the Hosnian system, when it cuts to Finn loading gear onto Ithano's ship he stops at the top of the stairs and turns to watch the sky. The blaster's strap is beside Finn's neck slung crossbody, but in the shot from behind there's no strap near his neck. (01:10:20)
Continuity mistake: After the First Order has destroyed the Hosnian system, including Hosnian Prime, Finn rushes up to Han and asks him where Rey is, and when it cuts to the shot of Rey running in the forest it's a flipped shot - note the leather cuff is on Rey's right wrist, etc., then in the next shot the cuff is on her left wrist as it should be. (01:11:05)
Continuity mistake: When Maz Kanata shows Finn, Han and Chewie the lightsaber, watch the blaster strap on Finn's shoulder. When Maz is saying "Take it. Find your friend," the strap is shown on his shoulder. Finn then takes the lightsaber and the strap is suddenly closer to his neck. Then a couple of shots after, the strap is suddenly back to its original position again. (01:12:00)
Continuity mistake: At the Resistance base, when the doctor's treating Chewie's injury, she's using a medical device with her right hand as she's telling him that he must be so brave, but when it cuts to the next shot it's her left hand up using the device. (01:22:55)
Continuity mistake: When Rey wakes up restrained as Kylo Ren's "guest" at Starkiller Base, Kylo Ren's mask has distinctive surface markings and a hole, but when he removes his mask and sets it down in the closeup it's a flipped shot - the marks and hole have switched sides. (01:25:50 - 01:26:25)
Continuity mistake: When Kylo Ren interrogates Rey, he removes his helmet and sets it down on a table of ashes. This table is not present in any of the wider shots of the interrogation room. [Director JJ Abrams has stated that the closeup of the ashes (the ashes of his victims, apparently) was actually from an earlier scene taking place in Kylo Ren's quarters on the star destroyer, which explains why the table is not visible in the Starkiller Base interrogation room. Still a mistake but there's the reason.] (01:26:25)
Continuity mistake: When Kylo Ren is trying to read Rey's mind, there is a closeup of Rey saying "Get out of my head!" During this shot, there are tear streaks running down her face. In the rest of the scene, these tear streaks are gone. (01:27:40)
Chosen answer: The actors playing Rey, Finn, Poe, and Kylo Ren were mostly unknown, while Mark Hamill is famous worldwide as both a screen actor and voice actor. The billing order was likely based on their fame and then on their new roles. It's not a union thing, minimum wage in the Screen Actor's Guild is far lower than what they were paid. It's a combination of bigger star, better agent, and the future of the series.
Greg Dwyer