As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURN BACK DUE TO NO NAVIGATION INFO ON ND. FMC LT & RT NORMAL. CURRENT LEG FAULT FMC-L FAIL INTERMITTENT AND FMC-R INTERNAL LOW PRIORITY FAILURE. REPLACED LEFT AND RIGHT FMC€™S REF AMM 34-61-01. VERIFIED CORRECT SOFTWARE PART NUMBERS ON CAPT AND F/O MCDU€™S REF AMM 34-61-00-752-101. PERFORMED GROUND TEST ON LEFT AND RIGHT FMC€™S REF AMM 34-61-00-745-222. BOTH LEFT AND RIGHT FMC PASS.