Fading Score -- How does it work?

[MikeFulton]

Most of the time I've been playing FX, I just do the regular table play, or occasionally I'll do one of the events. But recently I decided to try to work my way through the Questlines. It's mostly going okay so far but there's something I don't quite understand.

One of the various challenges you have to do is the "Fading Score" where you have so much time from the stat to build up as many points as you can, and when the timer expires, it starts subtracting points at a certain rate.

From that point, it's a race. You have to keep adding points to your total faster than the timer takes them away. If you still have enough points after 120 seconds, then the game keeps going and counting towards 150 seconds. If you reach 150 seconds and have enough points remaining, then you get to keep going until you hit 180 seconds.

I regularly get within a few seconds of that, but then the game ends even though I still have a lot of points remaining.

I thought it was supposed to end when the score fades down to zero, but apparently that's not how it works.

Does anybody know what I've missed here?

TIA!