When Joel references the painting and asks "What would you like to do with this," he puts his hands on his hips. When the camera changes angle, he now has his hands folded in front of him.
Before Sheila and Joel walk into Chris and Christa's house, Sheila is wearing obvious, big golden earrings. The earrings are gone when they enter the house, but visible when Christa catches them in her home. After that the earrings are no longer there.
When the Environmental Club is gathered into the classroom, the chalkboard changes dramatically between the first time that we see it and the second, with no reason for the change.