As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT#2357, EWR-MBJ. (AIRCRAFT PERFORMED AN AIR TURN BACK TO EWR). 'HYD B RSVR LO LVL ECAM IN FLIGHT LOST ALL FLUID IN BLUE SYSTEM; UPON INSPECTION OF THE T FITTING ASSY WHERE THE ELEC PUMP PRESS. SWITCH(2074GJ) IS INSTALLED, FOUND THE O-RING OFF THE PRESSURE SWITCH DAMAGED. REMOVED AND REPLACED O-RING IAW AMM 29-12-17 & OPS CHECK & LEAK CHECK GOOD. A/C OK FOR RETURN TO SERVICE.'