So I found this online and I'm not here to Toyota Bash But I thought Toyota Fixed this a couple years back. Initially Toyotas response was that they couldn't find braking issues, not it seems there are two different stories. Either A) Nitrogen is leaking back into the system, which makes no sense or B) According to Toyota Brake pressure parts are cracking.
Prius Brake recall
Alternate reason for recall
Prius Brake recall
Alternate reason for recall