Other mistake: When the characters go to the Himalayas, the whole time, like for 20 mins, including the confrontation scene, they are all wearing casual, short-sleeved shirts. You can see Mr. Burnish's henchmen wearing winter clothing, while the main characters don't freeze to death. They only start getting cold after a long time.
Continuity mistake: After the alien abduction, Emmet plans to lead a rescue mission and opens the gate asking "Who's coming with me?" During the sequence, the shadows change completely. At first he is not casting much of a shadow, then it reaches the metal doors, then it stops midway towards it. (00:20:55)Sammo
Continuity mistake: Max (the white and brown dog) has a brown spot on his eye that keeps switching sides throughout the entire movie.
Factual error: A blunderbuss is fired at a safe. The shot not only bores a hole into the safe but also blasts it out of the window behind it. First, a gun can do no such thing; a cannon can. (The film already establishes that the safe is incredibly heavy.) Second, the hole on the safe is wrong. It is gouged outward as if by an explosion from within. (00:38:10)FleetCommand