What is the ruling on praying behind imams who make mistakes in reciting Al-Fatiha, such as substituting some letters or omitting the tashdeed? Is it permissible to pray behind someone who utters inappropriate words inside the mosque? And what is one obligated to do towards someone who does not accept advice or desist from these actions?

Those who do not observe the sanctity of the mosque and raise their voices within it should be advised and educated about the etiquettes of the mosque. The mistakes of imams who make errors in their recitation should be corrected, and they should be taught correct recitation, because obvious errors (laḥn jalī) that change the meaning in Al-Fatihah invalidate the prayer according to the majority of scholars. If the imams do not respond to the advice, it is preferable to move to another mosque. If that is not possible, praying at home is better than praying behind an imam who makes an invalidating error, and the reward of congregational prayer can be attained by praying in a group at home.