When the scheduled task "cleanup: orphanrecords" runs while a customer is in the ordering process, the order record is removed completely from the order_item table.
I assume the order record uid is saved in a pending state, waiting until the order is completely finished. Until that moment, the order record appears to be an orphan.
It's an older version of Cart, 8.6.1.
And TYPO3 version 11.5.37.
Not sure if it's still relevant.