Suggested fix (unconfirmed): Enter the area from the cliff side with the door at the wall to trigger the doors to open. Alternatively, complete all Lone Splinterstar quests to unlock the tower.
Suggested fix (unconfirmed): Disable VSync and cap your frame rate in the Nvidia Control Panel. Lower the shadow quality and object detail settings in the game menu.
Suggested fix (unconfirmed): Find and defeat the boss "Gorehammer Kanuman" in the "Gylden Archives" dungeon. Complete the hidden dungeon quest she mentions to progress.