PAM_Succeed Unknown User

I'm getting:
pam_succeed_if(sfcb:auth): error retrieving information about user 52a3414e-206e-d68b-4eb7-20e9d3b5fab
... in my syslog. I think this may be related to a windows AD account, but it does not look like a user's SID which usually starts with a S-1-5-etc, etc. Any idea what this number may be so I can track it down and fix?
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