When the Heffleys are getting back into their car after losing most of their luggage, Greg gets in behind the driver's seat, but in the next shot, he is behind the passenger seat and Rodrick is behind the driver's seat.
The toiletries disaster leaves them with a mess that isn't consistent from one scene to the next (body, clothes, hair).
The mud of the van appears/disappears between shots.
When the van dies it's only partly up the hill when they begin pushing it, it's at the top.
When the Heffleys are at Corny's, Frank is seen wearing a tie when they first walk into the restaurant however when they are seated at the table his tie disappears.
The Heffley family stays the night at a motel. Greg Heffley attempts to dry his hands on a towel hanging on a rack in the restroom. After he realizes that the towel is wet, he drops it on the ground. Shortly after, the towel is seen on the rack again.
There are no headrests in their minivan which were removed to make those in rear seats visible.
At the beginning of their unplugged road trip, Frank keeps turning the wheel even though he's not turning. He simply turns the wheel while going straight.
When Rodrick finds his drumsticks on the side of the road, he screams, "Whoo! Every silver lining has a cloud!" but his mouth is clearly not speaking the words.
A human arm can be seen tossing items out of the boat.
At 1:01:30 into the film, the Heffly's begin losing their load from the boat. The crew member's hand can be seen while several items are thrown from the vehicle.
The GPS says it will take 47 hours to drive to Indiana. The furthest of the contiguous 48 states away from Indiana is Washington, which is a 32-hour drive away. And furthermore, as the Heffleys are leaving the country fair, there is a Georgia state highway seen.
Fall foliage is seen throughout the film, which is set during the summer holidays.
When Greg looks at the atlas with Rowley, it is implied that Meemaw lives in Crawfordsville, IN and that Player Expo is in Indianapolis, IN. In reality, the cities are about 50 miles apart from each other, but during the road trip in the film, it is implied that they are much further apart.
Frank is seen wearing a tie at Corny's even though there is a strict no tie policy however later on when the Heffleys are seated at the table his tie disappears he likely removed it to avoid having it put up on the wall of shame.