Deliberate mistake: The Fremen wear "stillsuits" to conserve their water, yet leave their heads completely uncovered. This would result in quite a bit of water loss through perspiration. (In the book, they wore hoods, masks and nose filters, leaving only the eyes uncovered, but it wouldn't work in a movie to have all the actor's faces obscured!).
Deliberate mistake: As David runs from the MPs in the restaurant, he jumps off the balcony onto the bar below. It is very obvious that it's the stunt double for Michael Pare doing the jump. (00:45:35)
Deliberate mistake: Dr. Chandra returns to the Leonov at the end of the film with the device that Dr. Floyd designed to cut HAL's memory circuits. He hands the device back to Dr. Floyd, who tosses it in the air and catches it when it falls back into his hand. One problem - there was no gravity on the ship at the time. (01:44:00)
Deliberate mistake: When Supergirl flies out of the lake upon her arrival to Earth she's wet. When she lands on the shore she's suddenly dry.
Suggested correction: Incorrect. She's not wet when she comes out of the water. She emerges from the water dry in an (incredibly wonky) effects shot. Why she's dry coming out of the water is unclear, but it presumably has something to do with the teleportation process for how she got to Earth considering her costume also suddenly appears on her as well.
Deliberate mistake: At the end of the film, when Alex, Maggie and Grig take off in the Gunstar, the crowd of trailer park residents watching them leave backs into the covered portion of the restaurant, right next to the 'Starfighter' game cabinet, which is readily visible in the shot. Mrs. Rogan then wonders where her younger son, Louis, is. The shot changes to show Louis pulling a bench up to the 'Starfighter' game to play it as dust from the Gunstar liftoff kicks up next to him while he watches it fly. Yet the crowd is nowhere to be seen in the shot of Louis playing the game despite everyone being huddled right next to it on the patio (his mother was standing next to it and should be able to see him). Given the proximity of the crowd to the game a moment earlier, Louis wouldn't be able to play it, let alone put a bench next to it. It's clear the filmmakers chose the image of the younger kid aspiring to be like his brother by playing the game over the logic of where the game was in relation to the crowd.