NHTSA Complaint #11563044 — 2012 BUICK ENCLAVE

I purchased this vehicle (used)on 01/12/2021. 5 weeks later the brakes pedal went to the floor. It has done this randomly several times. Usually I can get the car stopped, put it in park and pump the brake pedal a few times and the pedal will be back to normal.When this happens it's usually at a low speed and I can get the car stopped but it takes a while. I have attempted to talk to Gen. Motors at Detroit seeking information as to how can I repair this problem. I got no help from Detroit. My local Buick shop manager tells me it could be any number of things. Maybe a sensor or something in the brake system or a vaccuum problem. I need to know what to do to fix this problem before I get into a wreck.