Laravel orderBy back up field incase primary is duplicate

Working on a queuing system that allows users to book appointments.

There is a slight issue at the moment where two appointments can get the same value for a field of 'estimated_booking_time'. This time is used to show when they are coming up.

The problem is that when fetching all appointments the ones with a duplicate estimated_booking_time are then ordered by their ID which (depending on when the appointment was booked) can sometimes be in a reverse order.

Im using carbon to create a diffInMinutes return on another field but the where the ID is the backup order my results are not always correct.

Is there a way to tell Laravel instead to use another field as the backup orderby field when there are duplicate values?

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