As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON CLIMB OUT PASSING 23000 FEET, WE SAW "SINGLE FMC OPERATION" AND VTK ON F/O NAV DISPLAY. THIS OCCURRED TWICE AND THEN WE REGAINED DUAL FMC OPERATION. OCCURRED AGAIN ON DESCENT THROUGH 270. IT REESTABLISHED ITSELF AFTER 30 SECONDS. GROUNDED - YES. ACCOMPLISHED B737-800 FIM 34-61 TASK 836 FMC RESET. OPS CHECK NORMAL.