Aborted Process instances are not being deleted by the 'Delete Process Instance' job.
Before proceeding to remove stuck processes, allow time for the 'ABORTING' processes move to 'ABORTED'.
If there are many processes in the queue, it could take time. If they remain, there are two options.
This can help to move the stuck processes. If they still remain in the 'Aborting' status after a restart, proceed to the next option.
Refer to article: Delete Process Instances With No Finish Date
Refer to article: Processes stuck in Aborting status for long time