Continuity: During Grandpa's first scene, his cigarette and beer swap hands briefly.
Continuity: In a scene where Max and Ariel are having a conversation near the kerb, Ariel is loading things into her Jeep. You can see that the windshield wipers are in the stopped position to the right hand side of the front windshield. The shot changes briefly, when the Jeep is in view again during the same conversation the wipers are stopped to the left position.
Continuity: When grandpa sings the lullaby to Allie and she falls asleep there's a close-up of her face with her hair messed up and covering her face. The next shot is a long shot and her hair is neatly drawn behind (like in a ponytail).
Revealing mistakes: In the scene where Catfish Hunter is hooked and pulling the boat through the water, the rear of the boat is up high enough to see that there is no lower unit (propeller) on the outboard motor.
Continuity: During the "Chicken Dance" scene, when the couple are fighting, the dancing doesn't match the music. The Chicken Dance has a specific set of actions for various points in the song - this was blatantly off.
Continuity: When John passes out from the alcohol at Rigettes resturant, Maria's robe switches from half falling off to wrapped around both shoulders between shots.
Continuity: When Gustafson puts the cat in Max's car, it makes holes in the imitation leather, but moments later the holes are gone.
Continuity: When Max finds Maria fishing in her boat they show him come around a bed of weeds in view of Maria, but a moment later in another shot his boat is just coming around the weeds.
Errors made by characters (possibly deliberate errors by the filmmakers): In the first movie Grandpa Gustafson says he's 94 years old. In the second movie he says he just turned 95. So less than a year has passed but somehow Melanie's daughter Allie aged 3 or 4 years.
Continuity: While John and Max are fishing for Catfish Hunter in tuxedos, Gustafson's reel switches from a casting reel to a spinning reel and back to a casting reel.