I'm on Day 4 at 9:00. This is just after bombing the armory and elevator. I go down to the lower elevator room, activate "Send Bug" to the vent, it shows the woman that I previously bound with a bug mention that it's loosening, and then I'm in a vent room with the new bug, but I can't activate either of the vents to move somewhere else. Just stuck in a little box. I'm on PC, Windows 10.
I don't remember what story choices I had made, but this is during my first playthrough.