When making custom advancements with multiple childs from the same parent, they seem to take random places from top to bottom.
The places are always consistent in the same exact datapack but when doing some minor changes it shuffles their positions for some reason.
I dont know if this could be considered more like a suggestion but at least there is definitely an inconsistency somewhere
I was hoping there would be some sort of order, it would make sense to name the ,json files in the order they should.

i used the Advancements Generator from this page
https://advancements.thedestruc7i0n.ca/
doing a minor change such as changing the datapack name (after disabling the previous one) will do the shuffle thing

EDIT
i found that the order is not totally shuffled but ordered in a cyclic chain then picks a random starting one to put in top, that might be useful when troubleshooting I guess