As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IN CRUISE VTK APPEARED ON CAPTAINS ND AND FMC DATA DISAPPEARED ON BOTH CDU'S. AFTER ABOUT 1 MINUTE, THE VTK FLAG DISAPPEARED AND FMC DATA WAS RESTORED ON BOTH CDU'S. GROUNDED - YES. PERFORMED FMC BITE TEST PER B737-900 FIM 34-61 TASK 801. BOTH FMC CHECK GOOD.