Why do some repeat orders not add items to the order basket?

Why do some repeat orders not add items to the order basket?

Switchboard enables users, including Call Centre agents and consumers, to easily replicate an order by selecting "repeat order," which exactly duplicates the customer's previous purchase. 

Reasons:

However, an order might not be repeatable if there have been changes to the menu, such as price adjustments or item removals. In such cases, the order process will need to be restarted.