I know exactly why and it’s not a bug but it’s a very compelling argument for something @insti has been advocating recently. The width of the yellow brick road is a function of its slope. So when a shallower spot is coming up it also means the road width will be shrinking. This is how we get the universal property that you transition from good side (green) to right lane (blue) to wrong lane (orange) to bad side (red, eep day) once per day. But when you hit a kink in the road and the road width shrinks, weirdness ensues. You can have situations like you observed, where the road shrinks so if you’re skating the edge you have more work to do on the first day of the shallow section. And then when the road becomes steep (and thus wider) again you may suddenly coast back onto the road, making your bare minimum amount negative. Anyway, so we monotonize that conservatively so you can just trust the table even though it’s the convolutedest thing ever.
This would all go away if the True Road, the thing you dialed with the road dial, was not the centerline but the critical edge. This is related to thinking of it not as a yellow brick road but a yellow brick halfplane, where the key thing you care about is the boundary between safe and not safe.
We will get there! Thanks so much for spotting these manifestations of our poor design decisions.
Short version: It happens because the critical edge is not monotone but we adjust the values in the table so they are monotone. So you can trust the table to give the true bare mins by each day.