Is it obligatory to repeat the prayer if the imam does not master the recitation of Al-Fatiha, such as one who pronounces "Al-ladhīna" as "Al-zaina" or "Iyyāka" with تخفيف (takhfīf/lightening), and does the same ruling apply if the error is due to missing teeth?

One who cannot recite Al-Fatihah well should not lead people in prayer, for the Prophet, peace and blessings be upon him, said: "The one who recites the Book of Allah best should lead the people." If the Imam omits a letter, or substitutes one letter for another, or makes a mistake that changes the meaning, and is able to correct it but neglects to do so, then his prayer and the prayer behind him are invalid. However, if he is unable to correct the mistake, then the validity of praying behind him is a matter of dispute. The correct view is that it is valid, but someone else should be given precedence. Some scholars believe that the prayer led by a stammerer who substitutes letters is invalid, while others believe it is valid as long as that is within his capacity, and this is the more probable view. Nevertheless, it is preferable to choose an Imam who has no such defect, as a precautionary measure. It should be noted that some people exaggerate in their recitation during prayer without justification, and the prayer is not invalidated if the Imam has not perfected the emphasis completely.