Does the prayer become invalid if a part of the body that must be covered during prayer is uncovered?

Whether praying alone or in congregation, if a part of the body that must be covered during prayer is uncovered unintentionally and is immediately covered again, the prayer is not invalidated. However, if the uncovered area amounts to a quarter of an organ and remains exposed for the duration of a rukn (such as the time it takes to say Subhānallāhi’l-azīm), the prayer becomes invalid. If a person deliberately uncovers such an area, the prayer is invalid (fasid). (Merghinani, al-Hidaya, 1/45)

Source: T.C. Diyanet İşleri Başkanlığı, Din İşleri Yüksek Kurulu