What user are you logged in as when accessing the server?
Are you unable to access via console/SSH as root?
EDIT: Sorry, I missed your last line saying it happens in console and SSH. So are you able to log in via SSH using root? That should overcome the sudo problem.
Also, via the webgui system shell (at the bottom of the ‘System’ menu, I am able to log in there as admin and su to root fine. I’m using v4 of Rockstor.