As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURNBACK - AT 41000FT ON CRUISE, LEFT BLEED TRIP OFF LIGHT ILLUMINATED A TOTAL OF 4 TIMES WITH SUCCESSFUL RESETS ON EACH OCCASION. RIGHT BLEED TRIP OFF LIGHT ALSO ILLUMINATED TWICE AND CABIN BEAN CLIMBING. RESET WAS SUCCESSFUL. REMOVED AND REPLACED PRECOOLER CONTROL VALVE SENSOR, NR 2 ENGINE PRECOOLER VALVE, AND AIR CONDITIONING ACCESSORY UNIT PER MM.