At 1 :19:26 -there is not nearly enough salt for Mallory to encircle the tree.
During the dinner at the start of the film the Connect 4 grid changes between Ben lines. Although one might think this is actually because Nathan was playing the game, which isn't revealed until later, the change in disks is the red disks and Ben was playing red. Nathan was playing yellow.
At about 1 hour 14 minutes in, the director's feet can be seen in the shot.
As Ben is watching him through the window, Ty is mowing the lawn without the safety cutoff bar engaged. The lawnmower engine should not be running.
Within the 50 minute mark: Ben's Potter Bay Mariner T-shirt logo is inverted when he and Mallory are observing their neighbours.
Ben's "cast" is obviously made from elastic bandages, with the outermost bandage dyed blue.
At around 20 minutes -the "broken" lattice was obviously built to look like it was broken.
The Rubiks cube shown in the intro is a modern plastic tile version that did not exist "35 years ago" when the scene supposedly takes place. It would actually be a sticker tile version.
Earlier in the film Ben is playing Connect 4 with his father. He plays his turn dropping a red disc into the grid but he already had won (there's a diagonal line of four red pieces next to his move). However, there's a possibility he did not see it or call it.