Hi,
Have a look at this answer, make sure you have set the permissions on both the source and destination OUs - https://learn.microsoft.com/en-us/answers/questions/973272/delegate-help-desk-users-permission-to-move-users?comment=answer-975344&page=1#comment-1349105
Have a look at this article which will help identify the effective permissions for both the OUs and computer objects - https://nettools.net/how-to-find-active-directory-effective-rights/
I would also check that you have unchecked the accidental deletion options from the OU.
Gary,