Continuity mistake: Bond leaves M's offices, walks through the patio, and crosses a rounded pattern on the center. In the close-up, he's several meters behind, walking by the pattern again.
Continuity mistake: When M scolds Bond about the Mexico incident, the position of the newspapers on the table changes between shots.
Continuity mistake: At the start of the car/plane chase the road is completely wet. After the cars exit the tunnel the road is bone dry. When the cars turn off the road into the trees the road is completely wet again.
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)
Other mistake: After Blofeld taunts Bond, saying he has three minutes and the building will implode, he activates it. As M, Moneypenny, and Q watch, the charges ignite, three minutes and thirty seconds after Blofeld hit the switch.
Continuity mistake: When Hinx shoots at the plane he only shoots 3 times but the damage on the side shows 5 shots were fired. He's using a double-barrelled pistol which fires two shots at a time, so there should have been 6 holes - it's not accurate enough for two bullets to go through one hole.
Answer: It is mentioned that Oberhauser died 20 years ago. This could have been many years after James stopped living with him.