As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IN FLIGHT, BOTH FMC'S BLANKED FOR 30 SECONDS. VTK DISPLAYED THEN BOTH FMC'S RETURNED TO NORMAL. LOST VNAV/LNAV CAPABILITY-WAS RESTORED WITH FMC'S. NO FMC FAIL MESSAGES. GROUNDED - YES. MAINT MSG 34-69001 FOUND IN PRESENT LEG FAULTS. MAINT MSG 34-69001 WAS NOT ACTIVE. B737-9 IFIM TASK 34-61-00-810-836 COMPLETED AND FOUND TO BE AN INTERMITTENT FAULT.