Hi Michael ! I do not have to words to express my gratefulness towards you. The amount of time you took just to verify it its just amazing.
Few things:

1. You were right regarding the exporting settings to Modo: Triangles & Quads did much much better than N-Gons. I am experiencing a few artifacts in Modo, but fortunately Keyshot is not taking them in consideration, apparently.

2. The radius honestly I do not remember. I am almost sure did in Rhino. I have so so many files regarding this model and the try-outs that I am a little bit confused. Hopefully I will start to render today or tomorrow.

3. About the Bezier curve I am not sure if I understand it. I think I need to read you explanation a few times more. I am not sure why this model became so tricky. Summing it up this surfaces are rials coming from intersections between a rounded prism and planes. Then just two profile curves to generate the curves through the rials. I was not expecting that much hassle. I am aware this is not software related. I believe there is something tricky regarding the profile curves and the rials nature that make the calculation a little bit buggy.

I am expecting to find the way to re-generate this again with neater surfaces. I might change the profile curves to spheric sections and make a boolean. My friend and I just bought the CNC tip that will reshape the second prototype. We bought a semi-spheric tool tip in order to lower the cost and time of the cnc. I guess the next try-out will be booleans differences between a pipe and the cube. Hopefully that change will improve the quality?

Thanks thanks so much.