This is the response I got from my ticket:
Thank you for contacting us to let us know that incomplete orders are showing up on your Marketplace Sales Order history.
Under Construction orders happen when a user adds an item to their MKT Cart, but they haven't yet bought the item or removed the item from their cart.
Since these orders are not completed, they are usually not visible in orders logs on the Marketplace.
We have created an internal bug report for the Engineers so that they can fix the issue as quickly as possible.
Kind Regards,