What is the ruling regarding a mosque imam who merges the letter "ẓāʾ" with "ḍād" in the word "aḍ-ḍāllīn" in Surat Al-Fatiḥah and in the word "faḍarab"?

The Imam's pronunciation of the letter "dhāʾ" (ظ) instead of "ḍād" (ض) in the word "al-ḍāllīn" (الضالين) might be merely an illusion, in which case his prayer and the prayer of the congregants are valid. However, if it becomes clear that he deliberately substituted "ḍād" with "dhāʾ", then scholars have differed regarding the validity of his prayer. The more accurate opinion is that the prayer of the Imam and those who followed him is valid, due to the similarity of the two letters in sound and the reader's intention to convey the correct meaning, which is misguidance (ḍalāl) as opposed to guidance (hudā).