You need to open a support ticket to resolve but if I had to guess, it has to do with BCM changing the requirement to actually synch up user accounts that are using SYSTEM to authenticate with Active Directory. Way back when, you could create a username such as "Domain\username" and it would authenticate against a Domain Controller. Several revisions back, security methods were improved and now those accounts MUST be actually pulled in from a Security Group in AD to actually work. You may have some obsolete accounts that are failing this test.
Support will have the real answer and can assist with getting rid of those errors.
Thank you I will do that.