What is the ruling on praying in a mosque where the Imam frequently makes mistakes, given that other mosques are available?

The type of error was not clarified. If it was in Al-Fatiha and was a grave error that changes the meaning, then it is not permissible to pray behind him. However, if it was not so, but rather a pause in recitation or a lack of mastery in Tajweed (definition), then the prayer behind him is valid, even though the most proficient reciter has more right to lead, as the Prophet, peace and blessings be upon him, said: "The people are led in prayer by the one who is most knowledgeable of the Book of Allah." In this case, one can pray behind him or go to another mosque where the Imam is proficient. If the error was in a part other than Al-Fatiha, then the prayer behind him is valid as long as he did not intentionally make the error, but it is preferable to pray behind someone who does not make mistakes.