Plane Segmentation changed in 0.15.1?

### Checklist

- [X] I have searched for [similar issues](https://github.com/isl-org/Open3D/issues).
- [X] For Python issues, I have tested with the [latest development wheel](http://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](http://www.open3d.org/docs/release/) and the [latest documentation](http://www.open3d.org/docs/latest/) (for `master` branch).

### My Question

I implemented a RANSAC plane segmentation followed by a DBSCAN clustering similar to this: https://towardsdatascience.com/how-to-automate-3d-point-cloud-segmentation-and-clustering-with-python-343c9039e4f5.

It works fine in version 0.14.1
but in 0.15.1 it looks like this.
I can't figure out why, I already checked my code and the docs + release notes.

Start by reproducing the reported RANSAC plane segmentation followed by DBSCAN clustering with the linked example under Open3D 0.14.1 and 0.15.1. Compare the resulting point-cloud segmentation and investigate the version change; done means identifying whether the behavior is an intentional change, a regression, or a usage issue.

Written by the indexing model from the issue text.