Complaint about oral exam
You do not have your answer in writing at an oral exam and it can be difficult to document the nature of a complaint. Your complaint or appeal is based on your experience of the exam, which may differ from the examiner and the external examiner's experience.
Therefore your should write down a description of the examination process as soon as possible after the exam and attach the description as appendix to your complaint. Try to describe what happened from you went into the exam untill you left: "So I reviewed…" and "Then I said internal examiner…" etc.
If possible you can also describe how long you experienced each part of the exam took.