As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PASSING THRU APPROX 8000' MSL ON ARRIVAL QUICK SCENT OF BURNING PLASTIC (NOT OVERWHELMING) IN COCKPIT DISSIPATED QUICKLY. AT SAME TIME L AUTOPILOT EICAS AND DISENGAGED. AUTOPILOT REENGAGED UPON COMMAND AND NO FURTHER ISSUES. AS A PRECAUTION, REMOVED & REPLACED MODE CONTROL PANEL IAW AMM 22-11 & ALSO REPLACED RECIRC FILTERS IAW AMM 21- 25. ALL OPS NORMAL. REF LOGPAGE 1668960 FOR MSI STEPS C/W. (8316203) AIRCRAFT WAS GROUNDED.