I'll usually always kill all the attackers before the timer reaches zero. Did it again last night, in fact. On all my runs where this happened, I would get the "fight won" music-cue, but the game would stay in turn-based mode and the party would remain in their battle-stances. I then have to click End Turn a bunch of times (effectively skipping the remaining turns for the party and all summons) until the countdown reaches zero and at that point, the portal will disappear, Halsin will re-appear and the automatic dialogue sequence will start.
