Meaning of "otherwise"

Dear Teachers,

I’m pretty confused about what “otherwise” and “sag” mean in:

“She remembered the house with a pleasure. The steep walls on the house’s cliff, the way the house otherwise sagged comfortably down toward the approaching slope, its red roofs in the sun…”

Is it saying that the house would slide down the slope without the steep walls? Or it’s saying a different thing irrelevant to the previous sentence?

It says that except for the steep (straight) walls on the cliff side of the old house (or perhaps just the straight side of the house!), the rest of the walls (= the walls otherwise) lean (sag) far from the perpendicular.

It is evidently a pleasant old house, though it is now out of true.