Factual error: When first sucking a bullet from the wall into his gun, he then opens the previously empty magazine to find the bullet. Given he didn't work the slide (forwards or in reverse), the round should not be in the magazine, but in the gun's chamber ready to fire. (00:14:00)
Factual error: Oslo Airport - Neil is talking to the Protagonist on the bus. An American Airlines Boeing 737 can be seen behind the Protagonist. AA have never served Oslo, and if they ever were to, it wouldn't be in a 737. (00:37:08)