All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
The fatwa which we issued for you before and advise you to act upon is the Maaliki view in this regard, which is that the ablution of the person who suffers incontinence is not invalidated when the time of the prayer ends. This is more convenient and easier for you given the Waswasah (obsessive doubts) that your questions imply.
According to the view that the person who suffers from incontinence should perform ablution for every obligatory prayer, if he combines two prayers and the time of the first prayer ends while he is still performing the second, his ablution is invalidated. Some scholars held that ablution is not invalidated in this case, and this is the view of Ash-Shawkaani and you can act upon it. According to the view that this person's ablution is invalidated, he should perform ablution and the second prayer only, because the first prayer was valid.
Allah knows best.