Customer Education

Shoppers should be notified that they shouldn't pass products between each other, especially if they're not a part of one group (they entered separately).
Such behavior causes a "missed event" scenario – shopper A suddenly holds an item in the session, without any registered interaction with the gondola. Only in the session of shopper B it might be reviewed that the product was passed to shopper A.
This might lead to the product being charged two times and included on both receipts – when the shopper B picked up the product and when shopper A started holding the product.