Is the prayer of a congregant valid if he recites Al-Fatiha correctly, while praying behind an Imam who makes egregious grammatical errors (lahn jali) in Al-Fatiha, and advice has been ineffective with him?

The prayer of both the Imam and the congregants becomes invalid if the Imam makes a grammatical error (laḥn) in Al-Fatihah that alters its meaning and he does not correct it, because the prayer of the congregants is linked to the prayer of their Imam.