As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
COPILOT SIDE, RT BRAKE PEDAL GOES SOFT DURING TAXI. AFTER PEDAL WAS ALMOST TO THE FLOOR, RELEASED PRESSURE, AND BRAKING WAS RESTORED. THIS HAPPENED 5 TIMES ON A 2 MILE TAXI. R & R COPILOTS RT MASTER CYLINDER IAW MM CHP 32-42-01. BLEED SYS IAW MM CHP 32-42-20. BRAKE SYS, OPS AND LEAK CHECKS GOOD.