What was found
AT CRUISE FL390 W/ A/P B ENGAGED A/P DISCONNECT AND BOTH F/D'S TURNED OFF W/ NO WARNING. NO FAILURE FLAGS APPEARED. AFTER 30 SECS A/P A AND CAPT F/D RESPONDED. F/D ON FO SIDE WILL NOT RESPOND. FLIGHT CONTINUED ON CAPT F/D AND A/P B. AT LOC/GS INTERCEPT FO'S F/D CAME BACK. A/P B AGAIN WORKED. ALSO FO HDG BUG AND IAS/MACH MCP WINDOW UNRESPONSIVE. GROUNDED - YES. RMVD & RPLCD DFCS MCP - 9EA C/B'S PULLED & TAGGED, THEN ALL TAGS RMVD & C/B'S RESET TO ACCOMP THIS TASK. ACCOMP'D MCP INSTALL TEST AND LLM MAINT TEST FOR MCP - ALL ABOVE TASKS PER B737-800 AMM 22-11-34-000-801 AND 22-11-34-400-801, ALL OPS NRML. DFCS IS ETOPS SIGNIFICANT SYSTEM - GROUND VERIFICATION SUCCESSFUL, SEAMC DAN NOTIFIED.