Sooooooo.... I have a similar problem....
Though instead of waiting for my other characters, I moved off the trap, died, and my team mate revived me. Now, theres no picture frame, but theres a button on the floor. I've pulled the lever already in the priates office, I"ve scoured the place for anything, but I haven't found anything.
And the Black gate won't/can't be opened now?! Help???
After you pulled the lever in the office the picture on the wall in the office just besides the lever should become interactive/movable. Behind the picture is another button which reveals a trap door.
