Revealing mistake: Parzival heads back to the Halliday Journals to watch the scene of Halliday and Morrow parting ways again. There is glass between him and the scene and some camera angles show Parzival through the glass from inside with the scene reflected on the glass. However the reflection is wrong. Morrow is standing on the right with Halliday on the left, but when showing their reflection in the glass, their positions are not reversed. (00:23:45)
Revealing mistake: Just after Wade gets threatened and his home is about to be bombed, he leaves his van trying to call his friends. After this shot, the camera pans over a load of scrap cars. Whilst the movie is meant to be set in America, at least 3 UK registered cars are visible in amongst the scrap cars, still wearing their UK plates. These 3 rather unremarkable cars, a Ford Mondeo, Fiat Punto, and Ford Fiesta Courier van, are unlikely to have ended up in the US.
Suggested correction: Though unlikely, not impossible. This is a future scenario and it's not far fetched to think that some economic crisis prompted people to buy import cars and then never given US plates. Or they were imported for parts. Or some UK workers using their own car.