What is the ruling on the prayer of an imam who makes a mistake in reciting Al-Fatihah, such as by pronouncing "Ar-Rahman Ar-Rahim" with a dammah, and what is the ruling on the prayer of those led by him if they do not correct him?

If there is someone among the worshippers who recites better than the elderly man, then he has more right to lead the prayer. However, if they are equal in recitation, then the elderly man has more right to lead due to his age. Regarding the ruling on praying behind him despite errors in recitation: if the error is in Al-Fatiha and changes the meaning, then the prayer behind him is not valid. But if it does not change the meaning (such as pronouncing the letter "nun" in "Ar-Rahman" with a dammah), then the prayer is valid. If the linguistic error changes the meaning and he could have learned but was negligent, then it is not permissible to follow him in prayer.