Errors that can occur regarding deregistration are for example that the wrong domain name has been deregistered because the registrant requested the deregistration of the wrong domain name, or that the registrar indicated the wrong name. However, during the deactivation period and until the deletion date, the domain name can be recovered and reactivated.
Another scenario could be that the person who requested the deregistration does not have the right to make such request - The registrar must have appropriate routines to check a person’s identity. Make sure to save the information so that you can show for your procedure and make corrections if any errors occur.