As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CAPTAIN'S COURSE SELECT KNOB INTERMITTENTLY LOCKS. GROUNDED - YES. WITH A/C POWER OFF THE AIRPLANE REPLACED DFCS MODE CONTROL PANEL WITH SERVICEABLE UNIT. APPLIED GROUND POWER TO A/C. C/W DFCS MODE CONTROL PANEL ADJUSTMENT/TEST. TEST PASSED. REF B737-800 AMM 22-11-34.