Adprep was unable to check the specified user's group membership. This could happen if the FSMO role owner %1 is running ...

Adprep was unable to check the specified user's group membership. This could happen if the FSMO role owner %1 is running Windows Server 2003 or lower version of Windows.
[Status/Consequence]
Adprep continues upgrading your environment.
[User Action]
If Adprep fails, verify the specified user is a member of Enterprise Admins group and Schema Admins group if /forestprep is specified, or is a member of Domain Admins group if /domainprep is specified, or is a member of Enterprise Admins group if /rodcprep is specified.
Check the log file ADPrep.log, in the %2 directory for more information.

Adprep was unable to bind to any Domain Controller (DC) over Remote Procedure Call (RPC) in the Active Directory Domain %1. ... Adprep was unable to check the domain update status. Status/Consequence Adprep queries the directory to see if the domain ... Adprep was unable to check the forest update status. Status/Consequence Adprep queries the directory to see if the forest ... Adprep was unable to check the specified user's group membership. Status/Consequence Adprep has stopped without making changes. ... Adprep was unable to check the specified user's group membership. This could happen if the FSMO role owner %1 is running ... Adprep was unable to check the version of the operating system on the Schema FSMO %1. Status/Consequence Adprep has stopped ... Adprep was unable to check the version of the operating system on this computer. Status/Consequence Adprep has stopped without ... Adprep was unable to close a network connection to the Active Directory Domain Controller %1. User Action Check the log file ... Adprep was unable to complete because the call back function failed. Status/Consequence Error message: %1 User Action Check ...