When trying to perform a backup you are getting the error "Access denied"
The account specified for the restore isn't actually taken in account.
Specify the network credentials to access the problem DCs:
* Log on to RMAD box as xxxxxx
* Go to Control panel > User Accounts > Credential Manager > Add windows credential.
* Specify Internet or network address: Set name of DC
* User name: - Set the same account as you us in collection properties for accessing DC
* Password: specify password
This would force Windows to use provided accunt while accessing DC