Factual error: In the first scene where Dr Strange is preparing for surgery he uses improper surgical gowning technique breaking aseptic protocols. Strange puts on a mask after washing his hands, contaminating his clean hands by bringing them in proximity to the non-sterile environment of his face. Surgical masks must be worn before the full washing of hands. Another error is that he inserted his hands all the way through his gown to don gloves. Hands must never leave the sleeves and gloves must be put on with the sleeves still covering.
Factual error: When Dr Strange first exits the London Sanctum there is a blue USPS letter drop box on the corner. London Postal boxes are a different design and red.