Revealing mistake: As the gang drives up to the space-ship diner, cars are whizzing by in the background. When they are driving to the base there's also a clip of a fire truck going down the highway in the distance.
Other mistake: They have a great electric fence, but the power goes out because of the storm. They all panic and flee the house, but the lights are still on in the house.
White Light - S2-E2
Continuity mistake: When citizen Z is searching for zombies, he approaches a door holding a pistol with an under-barrel attachment. When he goes through the door, the attachment has disappeared. (00:01:05)
Factual error: Throughout the series, there are scenes of decapitated heads speaking with audible voices, in spite of the fact that they have no diaphragms, lungs or larynxes. Even if a decapitated head was somehow fully animate, it still couldn't utter a sound.
Character mistake: Doc holds the binoculars the wrong way round. (00:30:20)
Factual error: In a scene when the group is supposed to be near the east coast a Banner furnace and fuel truck explode, the problem is, Banner Fuel is only in Spokane, WA, on the west coast. Spokane is where the show is filmed.
Other mistake: About 10 minutes in, Doc cocks his shotgun. Then he does it again, and no shellcase is ejected.
Zombie Road - S2-E3
Other mistake: When Doc and Wrecking Ball have to jump out of the car to escape the Z's, Doc jumps from the passenger seat, but then several seconds later, Wrecking Ball (who is driving) also jumps from the passenger seat. While it's possible he shifted over the seats, it's more likely that the crew member we now see driving the car was in the way. On top of this double-jump-out-the-same-side issue, is the fact they end up lying on the road just a few feet from each other, rather than what should be well over 100 feet apart (based on the speed of the car).
Revealing mistake: As the team is headed to Warren's hometown the show shows a clip of zombies in the field but it's the same 12 people (exact same outfits too) used in 11 different places in the exact same shot.
Revealing mistake: At the end of the episode when they show Citizen Z, the computer on his left has data or some kind of code running down the screen. Right after he puts his glasses on, the pause button appears mistakenly on the screen, revealing that it's not legitimately a program running, but just a video the effects team setup.
Continuity mistake: Right at the end, after Cassandra throws away the finger, there is the scene with her "family" finding the music box. Cutting back to her; she again has the finger resting on her shoulder/hair.
Continuity mistake: When the lieutenant and the new guy that joined up in season 2 are in the hospital, he reaches for his gun, shoots, and...click. No ammo. The lady then pulls our her gun, slide fully retracted, finger not on the trigger and states "yeah, me too." Thing is - if the slide was already retracted from running out of ammo - wouldn't she already know? I mean, she holstered the pistol. More egregiously, every shot before this, her slide was not retracted, and the pistol was ready to fire, until now, when she suddenly has a retracted slide.
Factual error: When the group are heading to California after leaving the Missouri home of Lt. Warren they somehow end up in South Dakota. And go within 251 miles of Salt Lake City and then back track over the Rocky mountains to the facility in Fort Collins Colorado.
Other mistake: Doc is walking through a field listening to the radio. In the sky, center of the screen, an airplane is seen for about 8 seconds.
The Siege of Murphytown - S3-E12
Continuity mistake: Towards the end a woman is walking towards the fence completely covered in blood and guts, we see close ups of her boots, trousers and hands all covered in dripping blood. In the next shot she is still walking but her boots and trousers are clean and the blood on her hands is very dry.
Revealing mistake: During the opening credits, just before they discover the hotel, 10K fires a round from his rifle. This strikes a medallion hanging from Doc's neck and the bullet ricochets and kills a zombie. 10K ejects the spent cartridge from his bolt-action rifle. This cartridge spins in the air and lands on rocks; however, what lands is not a spent cartridge, but a live round, with bullet intact.
Audio problem: 10k pulls a knife to stab a zombie through the fence at the nuclear plant but they dub in the sound effect for a gun when he stabs the zombie.
Factual error: At the beginning when the group is at the USA/Mexican border and Vasquez fires his last bullet and then tries to fire again the recoil of his gun is shown, despite being out of ammo. (00:02:20)
White Light - S2-E2
Continuity mistake: Roberta is checking her magazine on the pistol and it's empty. In the next scene, without reloading, she fires 3 more bullets. (00:29:10)
Revealing mistake: The lady that is with the other two guys that kidnapped Murphy decides to remove her magazine from her pistol. It's an airsoft pistol. The magazine has a front feeding area for 6mm BBs, and looks weird in general. She also has no ammo, as you can see the entirety of the internal spring - not bullets. And the magazine is weird too.
Answer: When the plant zombies would attack they would wrap people with the vines and hold them, so they couldn't escape.