As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
HEADING BUG INTERMITTENTLY TRAVELS OPPOSITE DIRECTION COMMANDED BY HEADING SELECT KNOB. ACFT GROUNDED. DFCS FLT FAULT REVIEW SHOWED NO FAULTS LAST FLT. PERFORMED FIM 22-11, TASK 803 FOR MCP TESTS. ALL PASSED & PERFORMED DFCS LRU TEST FOR MCP. ALL TESTS PASSED IAW AMM 22-11-34. COULD NOT DUPLICATE PROBLEM. HEADING BUG & INDICATIONS OPS NORMAL ON BOTH CAPT'S & F/O'S DUS.