What is the ruling on an individual praying alone or a congregant praying behind an imam who makes grammatical errors ( لحن ) in his recitation, and what should be done in various situations, such as praying at work, at home, or in public places, taking into consideration the difficulty of leading prayer?

Scholars have differed on the ruling regarding congregational prayer, the validity of praying behind an open sinner (fasiq) such as one who shaves his beard, and also concerning the alteration of the letter 'ح' (Haa') to 'ه' (Haa') in Al-Fatiha. The Hanafis and Shafi'is permit praying behind an open sinner, though it is disliked (makruh (definition)), while the Hanbalis do not permit it. Changing "Al-Hamd" to "Al-Hamd" could invalidate the prayer. There is no harm in not praying behind such a person as a precautionary measure, and praying individually or with another congregation. You will still receive the reward for congregational prayer even if you pray outside the mosque. If you pray behind someone who makes a mistake, you are not required to repeat the prayer unless you do so as a precautionary measure. If the Imam's mistake (lahn) becomes apparent to you during the prayer, you may sever your intention to follow him and complete the prayer individually. It is permissible to pray behind an Imam whose condition is unknown in a silent prayer, and there is no need to investigate him. Your prayer is not invalidated if his mistake becomes apparent after the prayer, unless you were aware of it beforehand.