I discovered recently that drivers are allowed - without penalty - to reject an order when they reach the pickup location if they see the receipt and decide it is too far to travel [1].
As a customer you just see your food go: `Assigning Driver -> Driver En Route to Pickup -> Driver Arrived at Pickup Location -> Assigning Driver`, for two hours on repeat. Eventually your cold food arrives 2 hours later, and you are offered £5 credit for your ruined meal.
I live in Central London (Old Street), and have had this happen repeatedly with restaurants that are not far from me.
[1] = https://www.reddit.com/r/deliveroos/comments/82w97o/riders_o...