Devil's Details Bugged?

[axel15810]

Is an optional in this quest bugged or am I just not seeing how to progress? I did finish the quest, but after solving the light path puzzle in the top northwestern part of the map the puzzle the light still shows red even after solving and won't open up what appears to be an optional path to the north. This is the puzzle I'm talking about, seems like the northern path should open up but is not. Again, let me know if I'm wrong or am missing something.

The path circled in red appears like it should open up when the puzzle is solved.