Continuity mistake: In the first shot of the hologram of Endor and the Death Star, the Death Star orbits Endor in an counter-clockwise direction. In the subsequent shots, the Death Star orbits in a clockwise direction.
Continuity mistake: In the Special Edition, Sy Snootles (the lead singer of Jabba's band) is CGI, but in the original version, she was a puppet, looking a bit differently. In the first shot of the band sequence, you can see the old puppet singing on the stage. (00:11:50)
Continuity mistake: After Vader's shuttle lands on Endor, as the AT-AT is walking towards one of the ramps, you can see that the ramps are connected right next to the lift, under the landing pad. But when Vader exits the lift, there's a circular platform going around the lift, which wasn't there in the previous shots. (01:19:40)
Continuity mistake: When Lando is dangling from a rope over the Saarlac pit, he keeps moving up and down the rope between shots.
Continuity mistake: When R2-D2 is assigned to his duties in Jabba's palace, another droid (EV-9D9) says, "But you'll soon learn some respect." and her arm is in a different position from the previous shot. In the following shot, her arm is in its original position. (00:11:10)
Continuity mistake: Luke tells Threepio to tell the Ewoks that if our heroes are not set free, that he will use his magic. If you look on the right of the screen, Artoo is standing untied, even though at that point in the movie he had not been untied yet.
Continuity mistake: When Lando says, "Fighters coming in," a whole bunch of TIE fighters come towards them. There's initially a lot anyway, but then after about a second, two horizontal lines of 4 fighters appear from nowhere (centre screen, underneath the Super Star Destroyer). They suddenly just pop into existence, large enough that we should have seen them approaching. (01:31:20)
Continuity mistake: When the Sarlacc tries to drag Lando into the pit, the tentacle is grabbing his ankle in some shots. In other shots, it is wrapped around his thigh as well. (00:33:50)
Continuity mistake: During the battle between Luke and Vader, their sabers alternate between casting shadows on the floor, and no shadows. (01:52:40)
Continuity mistake: In the beginning of Luke and Vader's lightsaber duel, and also in a few shots right after Luke knocks Vader down the stairs, Vader's cape alternates between being draped behind and over his left shoulder. (01:48:55)
Continuity mistake: When Boba Fett falls into the mouth of the Sarlaac, he disappears just before the beak touches him. (00:33:45)
Continuity mistake: In the first shot of Chewbacca when he is in Jabba's dungeon with Han, his bandoleer is on the wrong side. (00:21:25)
Continuity mistake: When Luke wedges the bone into the Rancour's mouth, in the first shoot from behind, he holds the bone horizontally. In the beginning of the next shot, it is pointing upwards. (00:25:25)
Continuity mistake: In the scene where Luke and the others are trapped in the net, the dead animal changes appearance (both injuries and actual appearance) and position several times. For example, the animal seen when they are in the net has a different mouth and a bigger area of white fur from the one seen a few shots earlier. (01:08:35)
Continuity mistake: When Vader throws his lighsabre, it hits one of the supports holding the catwalk, but in the next shot, it is nowhere to be seen. (01:45:50)