When discussing the causes of the problem use open-ended questions. These are questions starting with “how”, “what”, “who” and “when”. By doing this you will encourage the employee to focus on the causes of the problem in a non-threatening way.
Remember that the employee is closer to the action than you are and may be in the best position to know what the real causes of the problem are.
When you feel you are making some progress, consider posing some questions to help the employee clarify the issues. Be aware that the employee may express some frustration with issues beyond their control.
Record the key issues raised in the discussion which will also help to demonstrate to the employee that you value their input.