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, ﷺ, is His slave and Messenger.
When urine or other nullifiers of ablution come out involuntarily and in an abnormal manner, two matters arise according to the Malikis. The first is its ruling as a physical impurity: is it excused or not? The second is its effect on ablution: does it invalidate it or not?
Regarding whether it is excused, they say: if it occurs every day, even once, it is excused when it gets on a person's body or clothes, and washing it is not obligatory, in order to remove hardship and ease difficulty. But if it does not occur every day, it is not excused, even if it recurs on some days. It is stated in Mawahib al-Jalil by al-Hattab: “...... But if it comes after a day or two, then it is not considered a persistent condition.” [End of quote]
As for its effect on ablution, it does not invalidate it if it persists for half of the time or more. However, if it persists for less than half of the time, it does invalidate it, because the matter of ritual impurity is graver and more severe than the matter of physical impurity.
It is stated in Hashiyat al-Dasuqi 'ala al-Sharh al-Kabir: “The upshot (of the ritual impurity) is that if it persists for all of the time, most of it, or half of it, it does not invalidate [ablution]; and if it persists for less than that, it invalidates it, while excusing whatever of it gets on [the body or clothes].” [End of quote]
Allah Knows best.