NEVER MIND, I figured it out. And for the benefit of anyone who might want to play TC19, I'm gonna explain what you're meant to do:
It is indeed a timing puzzle. There's one wall that comes down in front of the hallway directly opposite the terminal/buffer room; you have to walk past where it's marked on the map, then quickly fire a charged fusion bolt at the switch and run for the door at the north end.
Feels really obvious now. :U Though at least I wasn't the only person who got tripped up by that.