I managed to advance to (see heading) this section of the map without securing the round bio object that goes into the device that opens a force field in the office section of the 2nd floor. I beat all the Combine on the 2nd floor and the DINO Exhibit ground floor room, but have no way to get to the device that is also on the 2nd floor underneath the metal stairway. The 2nd floor doorway is blocked with alien growth, and there's no way to get to the 3rd floor to make may way there alternatively. I can't progress any further on the 2nd floor w/o getting the force field turned off, so I'm now stuck. Is this a bug or am I missing something besides the obvious.