Failed Demotion of 2008R2 DC

I migrated from a 2008R2 DC to a 2016 DC.  All FSMO roles moved successfully.  All queries return the correct values.  When demoting the 2008R2 DC it fails at "Active Directory Domain Services could not transfer the remaining data in the directory partition DC=ForestDNSZone...... to the new 2016 DC.  If I run a cmd for dsquery fsmoroleowner, it shows an old servername that was in place long before I acquired this client, possible failed migration.  I have scoured the DNS and ADSEDIT and found noting referencing this old DC name.   I am unable to find the old DC how should I proceed?  Manual removal of the current 2008R2?  How should I proceed?