Must one repeat missed prayers in which tranquility was not achieved, especially if ignorance of this condition persisted for many years?

If the lack of tranquility means a lack of reverence (khushu'), then the prayer is valid according to the majority of scholars, but its reward is diminished. However, if what is meant is the failure of the limbs to remain still for the required duration, then tranquility (ṭuma'nīnah) is obligatory in all physical pillars [of prayer]. If the prayer is performed with the minimum sufficient amount of tranquility, it is valid; otherwise, it is nullified and must be repeated.