Seed: 7683360502751022699

This is the world that I first noticed this "zipper" effect in the mesa terrain generation back in 1.7ish(snapshots? I can't remember.). I didn't make anything of it then because it didn't seem important and I figured that others who were more involved in bug tracking would catch it.

I didn't think of it again until I watched the first episodes of Hermitcraft Season 4 today. Their world has the same issue. The screenshots are from the seed in 1.8.9 and regenerated in 1.9 pre-3.