Factual error: If 2 spacecraft are travelling towards each other's planets, at the same speed, it would still take 6 weeks to get to each other's planet. They kept saying they must've turned back cause only 3 weeks elapsed.
Suggested correction: Where do you get it would take 6 weeks to travel to the other planet? Throughout the film they're constantly saying it's a 3-week trip to the planet and a 3-week trip back home, for a 6-week round trip.
Revealing mistake: When the lift body first separates from the orbiter you can see the support wires for the orbiter hanging below (scene must have been filmed upside down).