Yeah - this was our experience. The person in front went through and the scanner then paused for quite a while before it was ready for the next ticket.The one we went through took about 30 seconds between each time someone scanned a ticket (though I've seen someone post on NSC that this was controlled by stewards to slow down the rate at which we got through).
If you put a ticket in before it said it was ready, a message came up essentially saying "I'm not ready yet".
As you say, this really slowed down the flow of fans through that particular point.