As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MCP LOCKUP ON CLIMB -ALTITUDE ALERTING TONE/COULD NOT SILENCE -MCP ALT WINDOW INDICATING 50,000' PANEL UNLOCKED AFTER REACHING CRUISE LEVEL. GROUNDED - YES. ACCOMPLISHED BITE CHECK PER B737-800 AMM 22-11 TASK 803 OPS OK NO FURTHER ACTION TAKEN DEBRIEF.