Sometimes when the model in Blender, normals go haywire.
Any attempt to fix the normals recalculated normals recalculated outside or inside, fail.
This is the case exemplified in the image below
Just go on Object Mode select object and press keys Ctrl + A .
In that case you’ll be forced to reset transformations ( Ctrl + A -> Scale and Rotation to ObData)
See next image:
Next go on Edit Mode by pressing TAB key , and you will see the result.
… and I solved the problem