What is the ruling on the prayers of one who used to mispronounce the word "التحيات" in the Tashahhud by pronouncing the "lam" (ل) and "haa" (ح) with a sukoon and not geminating the "yaa" (ي)?

A melodic error (Lahn) that changes the meaning in the final Tashahhud invalidates the prayer according to the Shafi'is and Hanbalis, and this is the prevalent opinion. However, according to the Hanafis and Malikis, it is a recommended act, not obligatory. Therefore, whoever used to make melodic errors in the final Tashahhud can adopt the less preferred opinion that their previous prayers are valid and they are not required to repeat them, especially since Sheikh Al-Islam Ibn Taymiyyah holds that whoever omits a condition or a pillar out of ignorance is not required to repeat it. Nevertheless, one must learn the rulings of prayer and what its validity depends on, based on the saying of the Prophet, peace and blessings be upon him: "Seeking knowledge is an obligation upon every Muslim."