In season 3, episode 13. When Sandy walks in and gets his lucky tie from Kirsten, Ryan has a newspaper in his left hand. Next shot it's in both of his hands, then he has no newspaper at all, next shot he has the newspaper in his left hand again and the shot after he has a mug in his hands.
When Seth is talking to Summer, Seth is wearing a satchel on his left shoulder but at the end of the conversation there is no satchel at all