Brake Master Cylinder problems of the 2019 Toyota Prius

I was traveling at about 55 mph on highway 66 when the instrument panel began flashing the following warnings: "braking power low, phsb malfunction, parking brake low, pre-collision malfunction, anti-lock malfunction, lane deparrure malfunction, brake overide" . The only obvious symptom was that there was no brake boost - the brakes continued to function, but without power assist. I am a former auto mechanic, so I would have noticed if there were any other symptons. The dealership had the car for 3 weeks and ultimately replaced both the brake booster and the master cylinder. They initially replaced the booster and discovered that that did not fix whatever was causing the warnings and dtcs. Toyota instructed them to replace the master cylinder and that apparently fixed the problem. They could not explain why a fault in the master cylider would have caused the array of symotoms observed by both myself and the mechanics. I was surprized that the master cylinder was the cause as the the loss of boost seemed to be a brake boost problem. I was told that Toyota is aware of the problem and that it is widespread.