What was found
AIRCRAFT WAS NOT GROUNDED: AIRCRAFT HAD MEL 38-01D FOR WATER QTY INOP. AIRCRAFT WATER WAS TOP OFF AT DEPARTING STATION. DURING CRUISE ALL WATER STOPPED WORKING. FLIGHT WAS DIVERTED TO LHR. MAINTENANCE SUSPECTS FAULTY SOFTWARE: MAINTENANCE RELOADED SOFTWARE IN GPM R1 AND/OR R6.LSAPS 38 WW VLV OPS & 38 WW OPS RELOADED TO GPM R1.38 WW VLV OPS RELOADED TO GPM R6 REF AMM 42-21-02-00A-750A-A. FOLLOWED FOR TWO WEEKS WITH NO FURTHER FAULT.