Continuity mistake: In the first film, George refers to the tree that the family carved their names in as being in the front yard. In the second film, this same tree is referred to as being in the backyard.
Suggested correction: It is also established he can be scatterbrained when under strain, and he is often under strain, and there's no reason they can't have two trees for that purpose.
Continuity mistake: In the first movie, the wedding took place on January 6th. But in the opening sequence here the framed wedding invitation says October.
Continuity mistake: Franc gives George two Vatsnik and he takes them both at the dinner table. George asks Matty to pass the rolls. Matty passes them with his right hand. When the scene zooms out and Franc, Nina, and Annie come into the dining room, Matty's left hand is on the roll basket.
Continuity mistake: When they show the wedding invitation at the start of the film, Annie's name is shown to be "Anne Elizabeth Banks" and yet in the first film during the wedding she is presented as "Anne Catherine Banks".
Continuity mistake: In George's montage of memories, the girl playing Annie as a little girl looks completely different from the one playing little girl Annie in the original movie.
Continuity mistake: In the first movie Annie had lived in the house since she was five, something significant enough that they wouldn't forget. In the second movie, George and Annie had played their first basketball game at the house when she was four.