Kugelblitz - S3-E4
Revealing mistake: At the beginning of the episode, as Sissy is signing the papers under the pseudonym Dana Pocket, she is holding cash in her left hand. The words "pictures" "and "film" can be appreciated on the faces of the bills, revealing this is fake money, often used in Hollywood productions.
Chapter 7: The Reckoning - S1-E7
Revealing mistake: There's some sleight of hand involved when Cara gets her cup of tea from the repurposed IG-11. Maybe it was costly to have the animatronic arm working to the point of actually supporting the cup and hand it to her, so pay attention to what Cara actually does; Gina Carano is ALREADY holding the cup, taps the mechanical hand with it as if the fingers just released it from their grasp, and retrieves it. (00:11:50)
Revealing mistake: Angelica and the other children are about to crash through the door to attack Lyra and Will. As Lyra runs past a cabinet, a lamp sitting on top is knocked over and crashes to the floor. Dafne Keene, who plays Lyra, reached over and very obviously pushed the lamp to the floor.
When in Rome - S1-E3
Revealing mistake: Will and Frankie are in a boat. In the first wide shot the boat is going rather slowly, in the next shot they are speeding many times faster, and the shot is erratic, showing that the action was speeded up. (00:02:05)
Revealing mistake: Batwoman gets shot in the alley; the bullets create bad looking CGI sparks each time they hit her suit. When she gets back to the cave and sits down as Luke scolds her, you can see her suit bends and folds at the breastplate all rubber-like, making even more unlikely the fact that bullets would create sparks on impact (for what is worth, in the following episode there's a close-up of a bullet hitting the breastplate of the suit and there is no trace of sparks and not the slightest give from the material). (00:02:00 - 00:03:55)