How would a father bemoan his child who is always getting into trouble? He is trying to say:
It’s unfathomable to me how you have managed to spill wine on your white shirt.
Would it be undurchschaubar or unergründlich? Or some other word?
The word should not have the connotation of mysterious as in “The lord moves in mysterious ways”, which I think is unergründlich, because the father is speaking with anger and frustration.