Other mistake: Walt takes new-born Holly into the garage to show her the money hidden behind wall insulation. He enters through a door that doesn't exist in the interior of the house. (00:15:00)
Continuity mistake: When Hank arrives with takeout food from Los Pollos Hermanos, Walt picks up a container, but in the next shot he isn't holding it. Also when Walt places a chicken breast on Skyler's plate, it disappears in the next shot, but re-appears in the shot after that. There is a lot of back and forth with the food in this scene. (00:11:45)
Answer: Saul is a criminal himself. It's not past his capabilities to forge some documents to show the 857k is available.
Ssiscool ★
Forged documents by Saul is most likely the correct answer.
The_Iceman