What was found
DURING FMC DESCENT. FMC DID NOT FUNCTION PROPERLY IN VNAV. INSERTED ATC CROSSING RESTRICTION AT WAY POINT AND FMC DESCENT PERFORMED PROPERLY, ATC THEN DIRECTED SPEED INCREASE, UTILIZED SPEED INTERVENTION TO ADJUST SPEED. MODIFIED DESCENT SPEED CROSSING RESTRICTION AND FMC WOULD NOT RESUME & VNAV PATH, MAINTAINED VNAV SPEED. GROUNDED - YES. PERFORMED FMCS TEST NO FAULTS FOUND B737-800 AMM 34-61-00-710-801, VERIFIED CURRENT NAV DATA LOADED AT THIS TIME.