As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE IN ETOPS AIRSPACE, FIRST OFFICERS NAV DISPLAY WENT TO VTK AND SINGLE FMC OPERATION AND LNAV DISCONNECTED. FMC RECOVERED AND BLANKED A SECOND TIME A MINUTE LATER, BUT ONCE AGAIN RECOVERED BEFORE THE QRH PROCEDURE WAS ACCOMPLISHED. GROUNDED-YES. PERFORMED B737-800 FIM TASK 34-61-00-810-836 RESET FMCS CMPTR 2 & 1. OPERATIONS CHECK GOOD.