Hi RH,

Thanks for your reply, not a problem with the access, but when I like to work on something, that blocks it. 🙂

The problem part is not the caps; it is the flat/straight part; here, you need to increase the segments/subdivisions so the influence is different.
The calculation is difficult if there is no subdivision, so the Phong shading is typically "Broken." You can Unbreak this edge. (It must be a Polygon Object by then.)
Main Menu> Mesh> Normals> Unbreak Phong Shading

Let's try a different route, for simplicity:
Create whatever you need and place it into a Remesh, then perhaps in Subdivision Surface.
CV4_2025_drs_24_TXps_11.c4d

Is that a way to go for you?

All the best