NavMesh bake creates red obstacles in terrain for no apparent reason

Unity 2020.3.23f1

Baking a navigation mesh leads to red obstacle areas for no reason. The walking area is composed of simple 3d cubes; it doesn’t make a difference if they touch by snapping to grid or overlap. Making them bigger makes no difference. Adjusting any of the agent settings (slope, radius, step, etc.) makes no difference.

This is driving me crazy because I have another project with exactly the same setup and I do not have this issue. I can overlap geometry, line it up by snapping, whatever. It just works.

I do NOT want the walking path on the green ground to join with the brown path. I do NOT want the agent to be able to step off the brown onto the green. The brown and green areas are on different Areas.

The spheres here have no collider on them. They are not part of the navigation. They are not marked as navigation static at all; they’re just visual markers in the scene.

What am I doing wrong?

192207-wtf2.jpg

I just deleted the editor, upgraded to a new version, created a new project and now I have no issues. This seems like a bug of some kind.