As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE HEADING BUG LOCKED UP ON HEADING 336. UNABLE TO CHANGE HEADING. GROUNDED - YES. ACCOMPLISHED B737-800 FIM 22-11 TASK 801. DFCS BITE TEST GOOD. MCP LRU OPS TEST PASSED. ALL REQUIRED LLM TEST PASSED. HEADING KNOB ON MCP VERIFIED TO CHANGE HEADING ON MCP AND SELECTED HEADING INDICATIONS NORMALLY ON BOTH PDFS AND NDS.