I've had this problem previously but I was hoping that the DOT upgrade (from 7.2.4) and RLM update (from v 3) would fix it but it still exists.
When I try to log into the filer using the RLM connection, userid: naroot password: root password, it keeps saying that access is denied. The partner filer with the same settings works ok.
I've tried creating a local test user in the Administrators group and logging in with that but no go.
Here's a few other things you might to try just in case you are still having this problem ......
Make sure the root account is allowed all capabilities (*):
Toaster>useradmin user list -x root
Info: Default system administrator.
Allowed Capabilities: *
Password min/max age in days: 0/never
Also make sure that the root account is enabled on the storage system:
Make sure its set to on.
Eventually after many reboots of the rlm and some cluster failover / givebacks, it decided to start working. Unfortunately, there was no particular activity on my side that seemed to help.