What was the fault log ID with the most number of faulty parts?
SELECT T1.fault_log_entry_id FROM Fault_Log AS T1 JOIN Fault_Log_Parts AS T2 ON T1.fault_log_entry_id   =   T2.fault_log_entry_id GROUP BY T1.fault_log_entry_id ORDER BY count ( * )  DESC LIMIT 1
fault log ID with the most number of faulty parts refers to MAX(COUNT(parts)) in relation to fault_log_entry_id;