While the term "crack" might refer to a specific plugin name you heard, it is more likely you are looking for the industry-standard solution to avoid "cracks" (geometry failures) when rounding corners.
In SketchUp, "cracks" or missing faces during rounding typically occur when working with small-scale geometry or complex intersections. This happens because SketchUp's internal engine struggles to create faces smaller than approximately 1/64 of an inch (approx. 0.4mm) . Common Causes of Geometry "Cracks"
No, RoundCorner is the industry gold standard. However, the is a symptom of trying to force infinite resolution onto finite software.
No, the crash is related to geometry density, not the SketchUp version. Newer versions help with RAM management, but a poorly prepared model will crash in any version.
The "Round Corner crack" isn't a bug in your model—it is a mathematical limitation of SketchUp's kernel. If you remember nothing else, remember this: Make it big, round it, shrink it back.