For a few weeks, not all Royal Mail parcels <2nd class signed for> are updating to 'Delivered' status on Ebay.
Parcel posted last week, Royal Mail delivery status shows on their website as delivered the next day, with a signature & map showing delivery location.
On Ebay it has not updated to 'Delivered', remaining stuck at 'Dispatched'.
This is not the only sold item that has not updated to the correct 'delivered' status.
On the view order page, there is a 'tell us what you think' link, bottom right.
I've just done this, probably nothing will happen but I live in hope.
“We haven’t got a plan so nothing can go wrong!” Spike Milligan