Top-25 Rankings Issue/Error?

Doing a sandbox league, just finished week 1. I had multiple ranked teams get upset by unranked teams, only to have those ranked teams either not move down at all or even move UP in week 2. #25 moved up to #24 for example after losing to an unranked, and still unranked, opponent.
I even had an unranked team LOSE to a fellow unranked opponent, and that losing team wound up ranked #20.
So that leaves me with two questions. 1) why did this happen/what are the rankings actually based on?
2) in sandbox mode, is there any way to just do the rankings myself instead of the game doing it?
This is just very odd in what is an otherwise impressive game. Appreciate any insights that can be offered.
I even had an unranked team LOSE to a fellow unranked opponent, and that losing team wound up ranked #20.
So that leaves me with two questions. 1) why did this happen/what are the rankings actually based on?
2) in sandbox mode, is there any way to just do the rankings myself instead of the game doing it?
This is just very odd in what is an otherwise impressive game. Appreciate any insights that can be offered.