When Jack leaves his class to go talk to Grace, they are all sitting. As the angle changes we can see through the glass panel that they are all standing and talking to each other literally one second later.
When Will, Karen and Mr. Stine are sitting down for their second love stinks club, in close-ups of Karen, we see her bag is up on her chair to her right, on the seat. But in wide shots the bag has now jumped to the floor, beside the chair.
After Connie leaves Will's office, we see a stack of files on Will's desk, to his left. Then Grace enters his office, and now these files have vanished from the desk, and are now on the other side of the desk, to Will's right. In following shots they keep swapping sides.