In my limited experience, most Potentially Walked Units are caused by a lack of training or technical problems. We keep a binder at guest service where we keep the stickers with all flexible fulfillment orders after we've handed the items off to the guest. The binder has the order sticker, the time, date, and initials of the tm that completed the transaction. If we're not pressing "submit order" then we'll go back and investigate. But believe it or not, many tm's are forgetting to press complete order on the iPad after handing off the merchandise to the guest -- which means we lose out on that order when we go back to do the RTS and can't find some of the items.