By default, the plugin might use 6 or 9 segments. Lowering this to 3 or 4 segments creates fewer micro-faces, reducing the risk of SketchUp's engine failing to close the top surface.
Ensure the top face of your model is white (front face) and not blue/grey (reversed back face). Rounding plugins frequently miscalculate vectors on reversed faces, leading to torn meshes. To help you get this sorted out right away, let me know: sketchup round corner crack top
This gives you total control and eliminates the crack because the top face never touched the rounding algorithm. By default, the plugin might use 6 or 9 segments
Activate the tool and click on the quarter-circle arc. SketchUp will smoothly sweep that arc around the entire tabletop edge, creating perfectly manifold, uncracked rounds. If you want, I can: SketchUp will smoothly sweep that arc around the
Is the top face a or a complex, curved shape ? Share public link
Before running Round Corner:
Round corner doesnt work correctly - Extensions - SketchUp Community