As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LNAV BUTTON ON MCP DOES NOT ILLUMINATE FULLY. GROUNDED - YES. REPLACED DFCS MODE CONTROL PANEL PER B737-9 AMM 22-11-34 PG# 401. PERFORMED LLM MCP LRU REPLACEMENT TEST AND LAND VERIFY TEST, BOTH TESTS PASSED. ETOPS GROUND VERIFICATION SUCCESSFUL.