As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CAPT LT BRAKE INTERMITTENTLY MUSHY WHEN BRAKE APPLIED. BRAKE OPERATING NORMALLY FOR APPROX 2 SECONDS. AFTER THAT TIME, BRAKE PRESSURE DROP. REMOVED AND REPLACED PILOT LT BRAKE MASTER CYLINDER IAW CE 560 M/M CHAP 32-42-02. OPS CHECKED GOOD.