If your plugin is leaving "cracks" or broken geometry on the top face of your SketchUp model, it’s usually due to tiny geometry errors or a conflict with the rounding algorithm. Quick Fixes for "Cracked" Faces
If you are using the newer and encountering holes, the culprit may be the "Super Rounding" feature. This advanced option attempts to create an extremely smooth finish but can inadvertently create "tight" geometry that fails to form a face. sketchup round corner crack top
Extensions require clean input to generate clean output. Before clicking the tool icon: If your plugin is leaving "cracks" or broken
The designer had previously drawn a center guide line across the top face (to align leg holes). That guide line was a hidden, un-deleted edge. The Round Corner tried to round across that internal edge, creating a crack. Extensions require clean input to generate clean output