to the giant copy. Because the geometry is now large, SketchUp will successfully generate all faces.
Round Corner creating a "cracked" or faceted top surface? (Fix inside) sketchup round corner crack top
to draw a line across the "crack." This often forces SketchUp to re-calculate and close the missing face. After the face closes, delete the extra line. Alternative: Non-Destructive Rounding If you only need the corners to rounded in a final image, use a rendering engine like Asset Editor and select as the texture. Adjust the to the giant copy
If the top looks like it's flickering or "cracking" visually, you might have two faces occupying the same space. Delete one of the overlapping faces or move one slightly. Manual Healing (Fix inside) to draw a line across the "crack
The "cracked top" issue in SketchUp usually happens when rounding edges—whether manually or with a plugin like RoundCorner