The Shaykh (Al-Mufid), may Allah سبحانه وتعالى support him, said: "If someone is seated during ablution and has not yet finished it, and doubts arise that he might have invalidated his ablution or misplaced the order by performing an earlier act later or a later act earlier, then he must repeat the ablution from the beginning to ensure that he leaves the session having completed his ablution with certainty and free from error. However, if doubt arises after he has finished his ablution and left his place, he should disregard the doubt and rely on certainty. If he is certain that his ablution was invalidated by something that nullifies purity, or if he performed an earlier act later or a later act earlier, he must repeat the ablution from the beginning." What supports this is (following hadith):
Commentary #53