nothing sadly 
I don’t know what kind of modeling file it is? 
If it’s Existing modeling (previous attachment), it won’t be solved.
If you look at the wire frame, you can see the cause.
i don’t quite getchu 
, wdym modelling file ?
never heard of the term handmade modelling, what does it mean and what other kind of modeling is there ?
is there another way you can suggest to achieve the same result ? besides the blend file that you’ve sent which certainly improved the shading, although still had that crease in my previous screenshot…
It’s because the translator is stupid. 
To improve existing modeling files, it is possible in the same way as images.
However, it is not completely resolved and some problems are still visible.
It will be difficult to completely improve.
Using blender 4.3
gsdg.blend (915.2 KB)