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: When Luke and Vader enter the Emperor's throne room, they walk towards the stairs, and as the shot ends, Luke put his foot on the first step. In the next shot, they have suddenly moved further up the stairs. (00:26:45)
Continuity mistake: When Vader's shuttle exits the Star Destroyer in the beginning of the film, it is followed by two TIE fighters. The TIE fighters are far apart, but in the next shot, they're close together. (00:02:15)
Continuity mistake: When the Imperials are tricked into leaving the bunker, they are surrounded by Ewoks, and as the shot ends, if you look through the crowd, you can see that Han turns his head to his right. In the next shot, he's facing forward again. (01:46:55)
Continuity mistake: In the first shot of the Emperor's force striking Luke, the Emperor's hands are in a different position from the previous shot. This also happens after he says, "You have paid the price for your lack of vision." (01:50:30 - 01:51:10)
Continuity mistake: On the forest moon of Endor, when the stormtrooper punches Han, he falls and has a blaster in his hand but it disappears when he hits the ground. He can't have thrown it during the time he was falling, because he shot accidentally when he was near the ground. If he has thrown it, it should have been near him.
Revealing mistake: When the shield generator explodes, a piece of shrapnel flies towards the left side of the screen and then flies back, because it bounces off the inside of the building the miniature was housed in. (01:50:05)
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: 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.
Continuity mistake: After Vader enters the Emperor's throne room to tell him that Luke is one of the Rebels landing on Endor, as the shot ends, he is just about to walk up the stairs. In the next shot, he has already walked up the stairs. (01:03:50)
Revealing mistake: When Luke and Vader enter the Emperor's throne room, in the shot from behind, you can see the stairs through Luke. (01:26:30)
Continuity mistake: When Vader is searching for Luke in the dark, in the first shot, he is walking around a computer terminal, with the great window behind him. In the next shot, he's on the other side of the terminal, with the window in front of him. (01:47:10)
Continuity mistake: Before the Emperor gives permission to fire the Death Star, in the scene at the bridge of the Star Destroyer, the blue rank insignia of Admiral Piett and another Imperial officer is coloured black. This is probably caused by bluescreen effects replacing everything blue with the colour of space. This can also be seen when a Rebel ship hits the Star Destroyer at the end of the film.
Revealing mistake: In the scene where Han and Lando are talking in the hangar after the big meeting about the new Death Star, right when the scene opens and the shot pans down, notice how half the hangar is real and the other half is a matte painting. (00:49:30)
Revealing mistake: (Widescreen Only) The rancor puppeteer's arm can be seen on the far right side of the screen as it starts poking at a hiding Luke.