As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT FMC BLANKED AND DISPLAYED "VTK" FOR ONE MINUTE. RECOVERED AND FUNCTIONED NORMALLY FOR THE REMAINDER OF THE FLIGHT. GROUNDED - YES. ACCOMPLISHED B737-900 FIM 34-61 TASK 836. OPS CHECK NORMAL. SUCCESSFUL GROUND VERIFICATION ACCOMPLISHED.