I don't think it is solve-able without using teleport. If it is, than teleport should be blocked in that area.
It's definitely solveable, but maybe not solveable while visiting all rooms without Teleport.
And I have an interesting idea about that: Why should Teleport be blocked? Maybe if it was in the same condition it was in Braccus's day, but it isn't. Half the old structures on the island have been crumbling for over 1200 years. Why should it be just as inaccessible and impenetrable after centuries of neglect and decay as it was when it was intact?