Continuity mistake: After Madeleine tells Bond, "I love you," her right hand slides off his face. Cut away and back, and her hand is back on his jaw in a shot of her. We then cut to a shot of Bond, and her hand isn't on his face at all. It goes back and forth like that between shots.
Other mistake: When Bond enters the ruins of the old MI6 building, he encounters the plaque that lists all of those that gave their lives in service of MI6. In Skyfall, M mentioned this plaque, and mentioned that Silva's (the antagonist of Skyfall) name was Tiago Rodriguez, and that his name is on that plaque, and that she'd have it struck from the plaque. However, she never had the chance to do so within the timeline of the film (almost immediately after she said this, Silva escaped and tried to kill her at the government hearing, after which she escaped with Bond to Scotland, and died there). His name, however, is absent from the plaque, and there isn't even a gap for where his name might have been even if she *had* had the chance to have it removed. (02:03:55)
Continuity mistake: In the tunnel where Bond's Jaguar is wrecked by a truck it shows Moneypenny, Q and Tanner getting shot at, which shatters the right rear window where Q is sitting. Shortly after, they meet up with M to race away, and only a bullet hole is seen in the same right rear window of the vehicle. (02:02:20 - 02:02:50)
Factual error: The Number 15 London bus seen on Westminster Bridge at the end of the movie could not be there. The 15 runs from Trafalgar Square to Tower Hill.
Character mistake: Sciarra's (pronounced Shara) name is constantly mispronounced Skeeara, even by Italians like the priest at the funeral.
Factual error: When Q tells M that Bond is in Chelsea the screen shows "Austria." The names of the roads are stupid. One name is SEEKLAUSSTRßAE. If a road like this exists it should read SEEKLAUSSTRAßE or SEEKLAUSSTRASSE as the "ß" in capital letters is written as "SS" (at least in 2015). An other one is MÖSERNßTRASE instead of MÖSERNSTRAßE. Fun fact: Möse is a vulgar German word for a specific opening of the female body. (00:49:46)
Answer: It is mentioned that Oberhauser died 20 years ago. This could have been many years after James stopped living with him.