When Jeremy and Lizzy go up the stairs at Oswald's house, Lizzy's bag changes to an orange bag that she has with her on another day. It happens again when they go down the stairs.
When Jeremy and Lizzy are at the boardwalk, they aren't seen when the seen zooms out.
After the kids get 2 keys in the box, the second key isn't seen in the box where it had been put in moments before.
At Oswald's house he is seen picking up a remote to turn off the music very briefly, although in the next seen it is shown still on the piano.
When Maybel opens the package (the book) the back of the book is shown to be a Dear Canada book.