Revealing mistake: As the Enterprise nears the space dock doors there is an outline around the ends of the nacelles that precedes them as it moves. This shows that the ship was superimposed over the shot of the inside of the space dock.
Movie Nut
28th Sep 2015
Star Trek III: The Search for Spock (1984)
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Suggested correction: This isn't wrong, per se, but matte outlines are so inherent to this type of optical effect that it I think it would be like counting "makeup looks fake" or "unconvincing acting" as mistakes. There probably is a line where a special effect is so bad it can indeed be counted as a mistake, but this doesn't cross it, in my opinion.