Such occurrences are not common, but are not rare either.
In a real life cases - clients can be irrational and are many times biased against you. An interviewer can very well decide to put you under pressure to see how you take it.
You must understand that most interviewers would do this only on purpose. Think of it like a game. When an interviewer starts going rogue - just tell yourself that it's a role play where your role is to play the steely eyed consultant, while the interviewer tries to play a tough client.
If you set this psychology in your mind - such rounds can become easier to tackle.
Please message me with more details of what happened so I could suggest you some specific tricks.
PS: answers to your additional questions in the comment:
- "They ask a question…": Many people become highly unstructured when responding to this question. You must stay organized and stick to your framework when answering. Thats the first battle. If you have run out of all possible ideas, then you can confidently say that that is all. Be bold and confident in putting the pen down.
- “Prove it situation…”: Sure it may not be related. After all, no one is born with their future role in their mind. The key is to highlight qualities and learnings from that incident that may be relevant. The whole episode may not be as relevant
- “Strange business situations…”: You will often encounter clients that behave like that. If you are confident of your answer, then you should stand by it. However, doesn't mean that you should tell the interviewer that they are wrong. The objective is to showcase mediating skills and an approach that can help you resolve the conflict. Try to convince the interviewer and at the same try to see their point of view.