Revealing mistake: When Robert and Julie are attacked by snakes outside the cave, notice that in the shots when you see the backs of Robert and Julie there are hardly any snakes on the ground (I counted one) compared to other shots. The shots of Robert's leg as he sweeps the snakes away are almost certainly of a snake handler instead of the actor.
Continuity mistake: When Diana is being chased by Donovan after crashing her craft, she has her normal human eyes. But during Donovan's strangulation attempt she has lizard eyes. As we saw in the original series, a Visitor's human eyes had to be removed by hand before the lizard eyes could be seen underneath.
Continuity mistake: When the Red Dust is spread, there is a brief shot of some California citizens watching, and we see the Bernsteins among them. But the actress at George Mofogen/Mr. Bernstein's side is not Bonnie Bartlett, who played Mrs. Bernstein in the first two episodes.
Other mistake: After the transformation, Elizabeth is brought home. She lies asleep on the sofa. Who had the time to apply makeup to her? Her nails are shining, which means that someone has applied some polish on them. It is obvious that no actors (even male) will ever play without makeup; however, they should not have applied such an evident makeup to Elizabeth.
Continuity mistake: After a talk with Diana on the mothership, Lydia is left alone and then she takes a message out of her uniform. She wears a ring on her left middle finger and her nails are painted red. In the following shot we see Lydia's hands put the message into a box. The hands do not have their nails painted and wear no ring whatsoever.
Visible crew/equipment: When Diana and Lydia are walking in the mothership corridor there are two things to look out for. When Lydia first starts talking a section of the whitescreen appears in the top right of the picture. Then a couple of seconds later the shadow of the camera appears on the door to her left.
Revealing mistake: When Ham drives the van through the road barrier, the pieces fall off very easily considering how slowly he was travelling. In the next shot it is shown that the remaining barrier sections are both split vertically, revealing that they were sawed in the same direction beforehand, then the 'broken' pieces loosely affixed before the collision.
Plot hole: In the opening scene we see Mike and Kyle driving in the truck. Kyle remarks that Mike has been driving since midnight and it is broad daylight outside. So they have supposedly been driving for several hours. Yet they start talking about their mission as if they have only just got in to the truck. As anyone who has been in that kind of situation knows, everyone always discusses the important stuff at the start of the journey, so it is clear that the scene has been poorly scripted.