[JustBNme]

It seems we might be discussing 2 potentially related but possibly separate issues--one while already stopped--the other while coming to a stop.

The only issue I experience is while already stopped, and happens so fast that there's no time to "pump" the pedal another time. Like a normal "emergency" braking reflex, an increase in foot pressure already applied to the pedal suffices to stop the vehicle within an inch(es) of where it slipped.

In older vehicles, I've experienced the problem with a leaking master cylinder (and other brake line leaks, too), and agree that in such cases, the pedal will travel to the floor, requiring a pump or more to brake effectively. However, if that were the case here--and I don't necessarily think it is--then I'd expect:

1) the pedal should continue to go to the floor following each pump, and
2) there's likely to be some evidence of loss of brake fluid.

Someone experiencing the latter issue may correct me, but I have the impression the brake pedal pressure remains firm following that second application after one pump of the pedal. Thus, the mystery continues . . .