The Agent Of Year Zero - S4-E14
Revealing mistake: During the scene when Mr. Lyle is talking to the General (butcher character), his glove that he wears on his hand is removed to make a point about his thumb having been cut off. In the next shot, we see Mr. Lyle walking around the desk and putting his glove back on, and you can see his thumb folded under his hand as if the actor was trying to hide it and did not realize it could been seen from the camera angle.
Kingdom Come - S1-E6
Other mistake: At the start of chapter 12 in the episode "Kingdom Come," Frank returns home via taxi. In front of his house in Seattle, WA, there is a blonde woman walking a Rottweiler dog. This same blonde and Rottweiler can be seen walking by the crime scene in San Francisco in the "Gehenna" episode.
Plot hole: When Nicky goes into prison in Mexico to give a criminal a shot of insulin, two errors are seen. 1) The needle and syringe are far too big for an insulin shot, which takes a one ml syringe and a small sub-cutaneous needle. 2) When we first see the syringe, there is a small amount of insulin in it, but it grows the more times we see it, until a large syringe is two-thirds full - insulin is enough in a one ml syringe.