Does the ma'mum follow the imam if he makes a mistake and stands up for a fifth rak'ah?

Question:
Honorable Shaykh, may Allah grant you success. He says: The imam made a mistake and stood up for a fifth rak'ah in the Zuhr prayer. Some of the ma'mum sat down and did not follow him. He says: I have evidence that if the imam makes a mistake and stands up for a fifth, I sit down and do not follow him. Is his statement correct?

Answer:
Yes, this is the correct position. If one knows that he has stood up for an extra rak'ah, it is not permissible for him to follow him. If he follows him while knowing that it is an extra rak'ah, his prayer is invalid. Yes.