bchandler02

Hoping someone here can give some ideas. I'm not a GM guy but a family member has a 2017 Tahoe. Last week, after driving the highway for about 30 mins, then city streets for 10-15, they turned into a parking spot. When they did and hit the brakes to stop, the pedal went to the floor and it barely had any braking power. It has < 50k miles on it. Truck was towed back home and by the time it got back, everything was fine. Had a local shop look everything over and they couldn't find any issue. Also talked to a GM dealer and they had no idea as well. So far, nobody can explain why this ay happened only once. My first instinct would have been a failed master cylinder, but that would not explain why everything has been fine since. Anyone have any experience with this or ideas?