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.
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.
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.