Here is a case where legacy admin can lose completely control of the running Moodle :

As reconsidering mnet host table when recording peers after renewing the mnet_localhost_id in configuration, (problem of generating public key on Moodle 1.8.1 upgraded to 1.8.4), the mnet_hosts had a rotated id generated by an auto-increment, setting known hosts to 3, 4, 5 (regenerated once).

The issue is that mnethostid field of all user accounts has not been updated equally.

Admin account (id = 1) loses control and access in Moodle because forced manual account, and his mnethostid remained set to 1.

The mnet environement regeneration process should consider rekeying all mnethostsid of manual uses to the newly generated mnetlocahost id.