Other mistake: Among the credits for the film's music are "principle first violin" and "principle second violin." The correct word is "principal."
Other mistake: If Otto's wife was in a wheelchair for 40 years, why did the house not appear to be handicap accessible? Otto hadn't touched anything in the house after her death, but the only noticeable building alteration was the low counter top in the kitchen. No permanent ramps? No stair lift?
Other mistake: The movie begins with Otto buying 5 feet of rope. It turns out that the intended use was for him to hang himself. No way the hangman's noose we see was made from 5 feet of rope.