Is it permissible to separate from the Imam in intention from the beginning of the prayer, while following him in actions, if the Imam makes errors in Al-Fatiha, in order to avoid causing discord or embarrassment?

If the Imam makes a grammatical error (laḥn) in Al-Fatiha that invalidates the prayer, then he is not fit for Imamate. And whoever realizes this and fears discord (fitna), has the choice between praying behind him and then repeating the prayer, or intending to pray individually while outwardly conforming with him in actions. In this latter case, his prayer is valid.