We recently migrated our DC from SBS 2008 to Sever 2012 R2 Standard. We transferred the FSMO roles successfully and decided to keep the other server around as a secondary onsite DC. Today I logged on to run some verifications. When I ran NetDOM /query FSMO, it came back with the PDC and Domain Naming Master roles back on the old DC. No one here migrated those roles back to the old DC. I'm wondering if anyone here has experienced this and if so, do you know how and why this occurred. Searching through Google brought back little to nothing.
If you have AD Auditing enabled you will be able to see who changed this role back to the SBS server.