He forgot the order in which limbs are to be washed when doing wudu
What is required when doing wudu is to wash the limbs in the order that was narrated from the Prophet (blessings and peace of Allah be upon him). Based on that, whoever does these actions in the wrong order deliberately, his wudu is not valid. With regard to washing the right before the left when washing the hands and feet, that is not obligatory, because they are like one limb. The same applies to rinsing the mouth and nose whilst washing the face; it is not obligatory to pay attention to the order when doing them.