Character mistake: When Ginnifer Goodwin leaves the supermarket to go the parking garage, the green sign says 1 hour parking Customer's Only. It should say Customers Only, without the apostrophe.
Character mistake: When Harlan Edwards collapses and Dr. Arcane tells them to clear his airway, one of the other doctors addresses her as "Dr. Cane."
Character mistake: Shaun says that the underground facility is "built like a bunker", but the single missile they dodged just created a huge hole a moment earlier. (00:11:40)
Character mistake: The Captain's medal ribbon bar is sewn onto his uniform back to front, with the 1939-45 Star on his left and the 1939-45 War Medal on his right.
Suggested correction: This is explained in the final episode, as he took somebody else's medal ribbon bar in order to get into an event only open to "decorated" officers and hurriedly put it on the wrong way round. However, this is also a mistake. Although the Captain never left Britain, he would still be entitled to the War Medal and Defence Medal, so would legitimately have two of the ribbons he wears. And having campaign medals does not make one "decorated" in any case.