After switching Buck for the prisoner and when Buck first spoke to the android pilot, his necklace is first outside his tunic and then in the next scene it is inside his tunic. However, the next scene is set later. It would make sense that Buck was trying to smuggle something into the prison so that the guards would naturally confiscate it (and blow up after he had taken it off).
When Wilma and Buck walk into the bar together, Buck is still wearing the red prison bracelet that Sergio had previously removed. Actually, Sergio only removed Jen's bracelet as Buck did not have enough money to have both removed.
The sand falls up as Hugo is pulled under by the giant squid, indicating that the film was run backwards.
The prison robot throws a box, showing this to be a cardboard box painted silver, with an unpainted bottom.
The laser guns used are not the standard versions but a new and bulkier design. In some scenes when actors hold them, they very obviously point their index finger away from the hand grip and use their middle finger to activate the trigger. This is because the props department did not build this with enough room to fit all their fingers on the grip.
As the prison robot breaks through the gates at the space port, it can be seen that the gates were never mounted on the walls.
The rocks the guard is kicking while on the chase are made of cardboard.
When the sand squid engulfs Hugo the android guard, Jen Burton turns her head away in horror. This would be out of character for her, as she is supposed to be a hardened criminal and would presumably not feel a thing for the dead guard, whom she have loathed from the months she had spent in the prison. What's more, the guard was an android, not a human being.