Why does CC objects have visible edge/lines in game?

Hi all, I'm having an issue that I see with a lot of CC objects where the triangulated lines from the mesh is visible in game.
For example with this object I'm working on: Screenshot 

I know it's possible to change your Nvidia config. etc and that's all well and good, but why doesn't the lines show up on a normal Sims object?
What is the difference between my mesh and The Sims 4 mesh?

I've tried matching weight paint, checking for vertex paint, triangulate modifier after split-edge modifier and vice versa.
I just can't find the actual difference?

If I make my object by only taking and changing parts of a Sims object the lines doesn't show up. However for the process of texturing I remove all the triangles (decimate - planar) and then triangulate again at the end, and the lines are visible again in game.

I'm desperate to find the issue so I can actually make my objects from scratch and be as creative as I want without worrying about the lines in game.

Any recommendations for what I can try or if anyone actually knows why this happens, please let me know, thank you