As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
HEADING BUG WORKS INTERMITENTLY, VERBAL FROM CREW HEADING SELECT KNOB WAS INTERMITENT. ACFT GROUNDED. MANUALLY OPERATED MCP HEADING SELECT KNOB THRU ALL HEADINGS, ALL DIGITS AND DU'S DISPLAY NORMAL. CANNOT DUPLICATE DISCREPANCY. ACCOMPLISHED DFCS BIT CHECK AND MCP TEST ALL TEST NORMAL AND NO FAULT WERE LOGGED IAW FIM 22-11 TASK 801 & 803. NO HISTORY 30 DAYS.