Visible crew/equipment: After Bobby tells Alice that he can't pass Jan the potato chips because he's "not here", when Greg walks in and Bobby tells Alice that Greg's "not here either" we can see the tape mark on the floor behind Jan.
Continuity mistake: While the kids are practising the potato sack race as Jan watches from the sidelines, when Marcia steps into her sack and hops away there's a large color image on the front of the sack, but when she reaches Peter, then turns and heads back the image has vanished - it's not on either side, then it reappears when she's back with Bobby. Additionally, when Cindy hops in the sack that Greg was in, the sack is ripped at the bottom and Cindy's feet are on the grass, but when Cindy reaches Peter the bottom of her sack is perfectly intact.
Answer: The dangling bracelet was used for dramatic purposes - to keep the audience on edge.