As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LIGHTS ON VNAV MODE SELECTOR SWITCH ON MODE CONTROL PANEL (MCP) INTERMITTENTLY AND REPEATEDLY ILLUMINATED OFF FOR UP TO FIVE(5) - TEN(10) SECONDS AND THEN BACK ON WITH VNAV CONTINUOUSLY SELECTED, IN FLIGHT, ALL PHASES OF FLIGHT. MCP "IAS/MACH WINDOW REMAINED CLOSED AND "VNAV PTH" REMAINED INDICATED ON FLIGHT MODE ANNUNCIATOR PORTION OF PRIMARY FLIGHT DISPLAYS. GROUNDED - YES. REMOVED AND REPLACED MCP IAW B737-800 AMM 22-11-34.