As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CLIMBING THRU FL 300. AUTOPILOT DISENGAGED AND UNABLE TO RE-ENGAGE. AUTOPILOT B ENGAGED OK. LATER IN FLIGHT WAS ABLE TO RE-ENGAGE AUTOPILOT A. GROUNDED - YES. REPLACED THE DFCS MCP PER B737-800 AMM 22-11-34/401. OP CHECKS REQUIRED. OPS CHECK OF MODE CONT PNL GOOD. ALL LLM TEST PASS REF AMM 22-11-34.