I had some missing LEGO bits, so I found the components on ldraw.org, converted to STL with LDView, and butchered them together with Fusion360.
In this case, I merged 3 parts into one, so I’d only have to deal with 1 interface instead of 5. The sanding probably made it worse.
Wet sanding (with appropriate sandpaper) makes a huge difference, especially for smaller grid sizes.
But it’s probably easier to just get some individual pieces from Bricklink.