Continuity mistake: After Luke leaps up to the catwalk during the lightsaber duel, Vader's left shoulder is more covered by his cloak than in the previous shot of him.
Revealing mistake: During the lightsaber duel, Vader throws his at Luke. The catwalk behind Luke explodes, but if you watch in slow-motion there are two explosions: one some inches over where the lightsaber actually hits and one far on the left.
Audio problem: When the group in the shuttle Tyderium is waiting tensely to see if the clearance code is accepted, Han says, "They're not going for it, Chewie." If you look closely, you can see that when he stops talking, his mouth is still moving. (00:54:00)
Continuity mistake: In the Emperor's throne room, the existence and arrangement of several of the canisters on each side of the lift/elevator changes between shots, several times.
Continuity mistake: During the battle against the Death Star, right before the Emperor gives permission to fire the Death Star, Wedge says, "Red Three, Red Two, pull in." Another pilot answers, "Got it", but it is neither Red Two nor Three, but Green Leader. (01:36:25)
Revealing mistake: If you watch closely (or play it in slow motion) when the scout trooper punches Han, you can see that the troopers hand never actually comes into contact with is face. (00:55:45)
Continuity mistake: When Chewbacca gives Han a hug in his prison cell in Jabba's palace, he initially puts one arm around him, but as the shot changes both Chewbacca's arms are around Han.
Continuity mistake: After the Ewok takes off on the speeder bike, Han says, "You stay here, we'll take care of this." Leia turns and she can be seen with a very large smile, even showing her teeth. When the camera instantly cuts to a different angle of the scene, Leia is no longer smiling, displaying a deadpan look.
Continuity mistake: In the fight scenes on the skiffs with Jabba the Hutt's men, the skiff that Han and Chewie are on is hit with a laser blast and Han falls over the edge feet first, yet in the following scene he is hanging upside down with Chewie holding his feet.
Continuity mistake: When Han is planting explosives in the bunker, he says, "Throw me another charge." and places the charge on a crossbeam. In the next shot, the charge is on a different part of the ceiling. (01:47:00)
Continuity mistake: In the lightsaber duel between Luke and Darth Vader, Luke chops off Vader's hand twice before Vader falls down. The first shot shows Luke's lightsaber striking Vader's wrist, and Vader's hand separating from the wrist. The second shot is from behind and shows the lightsaber chopping Vader's hand clean off his wrist, then it sparks.
Continuity mistake: When R2-D2 is tied up in the Ewok village, the rope that binds him keeps changing position.
Continuity mistake: Just before the Emperor's ship lands on the Death Star, a formation of four TIE fighters disappears from the center right of the frame. This happens seconds before the in-hangar scene with Vader greeting the Emperor. This is visible on VHS.
Continuity mistake: After Lando is shot off the transport vehicle when Han is trying to save him, look for Lando to actually walk down the sand in the bottom of the screen. The very next scene, he is hanging on the rope.