Continuity mistake: During the fight with Zhou Cheng, Cheng does a forward flip and kicks Danny, making him stumble backwards. In the shot of Cheng lying on the ground, Danny is holding his stomach. In the shot immediately afterwards, he's holding his chest.
Continuity mistake: Spoiler! At the end of the episode, after Elektra decapitates Alexandra, the blood pattern on her changes changes when she turns around and asks "any questions?" Most noticeably more blood on her forehead and two streaks down her chin that suddenly appear. (00:49:10)
Factual error: In the opening seconds of the intro the BTK killer is following a woman home in his work van. Both the woman and BTK have license plates on the front of their vehicles. Kansas does not use front license plates. (Also, BTK's van shows the county abbreviation on the plate as WY - Wyandotte County - where Kansas City, KS is located nearly 200 miles away. The county tag abbreviation should be SG for Sedgwick County).
Factual error: This episode includes a segment about an abandoned dry dock in San Francisco. At one point, one of the commentators several times refers to the U.S.S. Ward as a "battleship," and marvels that it was built in 17 days. The Ward (DD-139) was a 1200-ton destroyer, not a battleship, and was launched after only 17 days, but then took another two months to complete. By way of comparison, the California (BB-44), an actual battleship of 32,000-tons built during the same time period, too nearly five years to complete.
Factual error: Johann Eck is dressed as a cardinal and Albrecht von Brandenburg addresses him as "Your Eminence" and kisses his ring. In reality, Eck was not a cardinal. Albrecht, however, was. It should be Eck showing deference to him, not vice versa. Albrecht was also only thirty, half the age of the actor playing him.
Factual error: The Navy Seals call in air support and provide a fire mission to given coordinates. The targets are engaged with rockets and gatling/chain guns. The UH-60 Black Hawk is shown leaving after the air strike. This UH-60 however only had mini-guns in the doors. The type of UH-60 needed for this action would be the UH-60 DAP, which is configured as a gunship and has no troop carrying capacity. The DAP can carry chain guns, mini-guns, missiles and or rockets. (00:03:00 - 00:03:23)