Baking Curvature from edited Normal Map

LostBeyonder

I am practicing with Substance Painter texturing this model download from Substance Share: https://share.allegorithmic.com/libraries/2087
When I bake a Normal Map and a Curvature Map from the high poly at 2k or 4k pixels of resolution, the results are correct. Both maps are smooth and without artifacts.
If I add some details in the Height Channel and bake a new Curvature Map from the Normal Map exported with the added details included (in TGA format), these "fibers" appear all over the new map:

 
I obtained the same weird result with the baker of Painter, the baker of Designer and the Curvature node in Designer.
Why does it happen? And how should I fix it?

Chimp

Your edits are degrading the quality of the heightmap that you create the normal and therefore curvature from, probably taking it from 16 to 8 bit in the process, causing stepping?

Jerc

Yes, you should use a 16 bits format to export your normal map, like png.