For those of us who have used a listing where the buyer has a choice of item based on color or size, be aware that if the listing automatically renews on a buy it now, there may be an issue.
It seems on the renewal that the original items and quantities are picked up. So if you have sold one of the items, make sure you have revised the listing and removed it from the choices before renewal or just cancel the listing and make the updates before letting it renew.
I do not know if this is a new glitch or how these listings are designed but I just had it happen to me. I had to cancel a sale and eat the defect because I thought when the listing renewed it would only show the ones that were still available.