I have been running into this issue for the past couple weeks now. The above fix does work (thank you!) but is not viable for production.
This does feel like a bug. These meshes appear to getting saved as World Partition actors when they should remain dynamic to the Landscape Spline. I think.
I thought maybe they were HLOD’s but deleting/ rebuilding HLOD’s did not affect them. Nor did rebuilding Lanndscapes, Spline Mesh actors or anything else. Below is a picture of the road in the editor:
And this is the “ghost” in PIE:
These guys are showing up on a lot of roads across a large WP landscape (16132x16132)
Hunting down the mesh on disk and deleting does work but is just not practical for a full scale production.