This seems to be a subtle off-by-one index error when drawing each colored 3-km segment of the hodo. The first data point after a segment cutoff is skipped when connecting u,v points. If z = [..., 2900, 3100, 3300, ...], then the u,v point at 3100 m AGL is skipped, since it's the first index after the 3-km segment cutoff. Only becomes noticeable with vertically sparse data.
This seems to be a subtle off-by-one index error when drawing each colored 3-km segment of the hodo. The first data point after a segment cutoff is skipped when connecting u,v points. If z = [..., 2900, 3100, 3300, ...], then the u,v point at 3100 m AGL is skipped, since it's the first index after the 3-km segment cutoff. Only becomes noticeable with vertically sparse data.