As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WE HAD A DUAL FMC FAILURE THREE TIMES (VTK/MAP) BIT IT CAME BACK EACH TIME. LOST VNAV DATA FOR GOOD THOUGH. GROUNDED - YES. ISSUE IS INTERMITTENT LT FMC, RT FMC HAD NO ISSUES. PERF FIM 34-61 TASK 836. OPENED, THEN RESET C/B A6 ON P18-2. L/H & R/H FMC OPS NML. ETOPS GND VERIFICATION TEST SUCCESSFUL.