we've installed NSM on a Windows 2012 Standard with Active Directory and forest level 'Windows2012Forest'.
The account doing the schema update is both domain and schema admin.
NSM Admin says that the schema is not extended

When starting the installation it says:
- Current Forest level 5 is good
- all three ccs- attribute/class schema extensions do not exist
- one or more schema extensions need extending

When start the action, the following error messages appear:
Stack Trace: at System.DirectoryServices.ActiveDirectory,ActiveDir ectorySchemaProperty.Sae
at ADSchemaExtension.AttributeExtension.AddToSchema()
Exception adding attribute to schema: The object already exists