What is the ruling for one who misses or mispronounces a letter of Al-Fatiha due to inability?

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Whoever omits a letter from Al-Fatiha due to inability or replaces it with another, such as a lisping person who substitutes 'Raa' with 'Ghain,' or one who merges a letter into another, or one who makes a pronunciation error (*lahn*) that changes the meaning, like misplacing the vowel on the 'Kaf' in 'Iyyaka' or the 'Taa' in 'An'amta,' and is unable to correct it, is treated as an illiterate person. It is not valid for a proficient reciter to follow him, but it is permissible for one like him to lead another like him, as they are both considered illiterate, allowing one to follow the other, similar to two who know nothing.