Undo the fillet. Delete the internal guide line. Soften the top face edges. Re-apply Round Corner. Result: Perfect, crack-free top. Conclusion The SketchUp round corner crack top is not a bug in Fredo6’s plugin; it is a symptom of messy native SketchUp geometry. While frustrating, it is entirely fixable. Whether you choose to manually stitch the missing face, use the Intersect Faces repair, or prevent it by grouping your top face, you now have the toolkit to defeat the crack.
A massive "crack top" appears 2 inches from the corner. sketchup round corner crack top
Why does this happen? More importantly, how do you fix it without scrapping hours of work? Undo the fillet