Other mistake: In the original version, in the first wideshot of the Super Star Destroyer, on the right side of the screen, the light of a Star Destroyer (but nothing else of it) can be seen just flying through space for two seconds before it disappears. This mistake is fixed in the Special Edition.
Other mistake: When the Millennium Falcon escapes Hoth and is pursued by the Star Destroyers, frantic movements cause them to collide. Watch the interior shot of the Star Destroyer as everybody is thrown around. Near the bottom of the screen one of the computer consoles comes away from the wall and is hurridly pushed back into place by a controller! (00:35:55)
Other mistake: After Vader cuts through a pillar with his lightsabre in the beginning of the duel, the hole in the pillar is much bigger than it should be. (01:37:35)