Hi there - having a version of these bugs, I think. I hacked my way through the keep (killing all the quest NPCs like Syri and Marte, I guess) after sneaking in with an Athletic check. I killed all the pirates in the Court and put a bomb in the harpsichord when I examined it after, thinking I was just being a troll.
When I encountered Lamond I'd already cleared out the underground docks, so we made the deal right there, I rang the bell (definitely NOT in stealth, and Aloth commented 'this is going to be loud, isn't it'), Benwith never came out, so I went downstairs and Lamond and friends had taken off in the Drake. I found my way into Aeldys' tower, killed Benwith, and now I can't get out of the keep. I don't have a rope and grappling hook so I can't climb down through the window that I came in through, and the windlass to raise the gate in the northeast corner does not appear to be interactive. As far as I can tell, I'm stuck.
