When Cheryl and Toni are in the bathroom, as soon as Cheryl leaves, the position of Toni's hand on her bag changes as the shots change.
When Veronica finds Archie and Andre talking in the woods, the bottom hook of her umbrella changes the direction it's facing multiple times throughout the scene.
Jughead and Archie are playing cards. They are all scattered out on the table. When Betty and Veronica walk in and the boys get up, the cards disappear.