There are always nosing lines on the models. Mostly it’s black lines but sometimes there are white lines too. I tried to set the highest Multisample anti-aliasing but it doesn’t clean up every edge. Does anyone have solutions?

Looks like the back face color bleeding through. This is a graphics card issue but you can edit the back face color in the style to minimize its impact.
This has bothered me for a long time as well, and I’ve always done what Dave suggested… color the back face to minimize the impact of that ‘visual noise’ sneaking through. I either color back faces black (to match default edge color), or match the color of the front face. This works quite well, even though it’s a bit of an annoying extra step.
[Note that you can manually paint back faces with the Paint Bucket tool, or use the Entity Info panel to drag-and-drop the front color swatch over the back color swatch to swiftly match them. This works nicely when you’ve pre-selected a bunch of faces you need to re-color all at the same time.]
Hi Dave, thanks so much for the solution! It does minimize the problem.

