Using Aspose diagram 20.1, converting the shape in results in a corrupt shape layout in SVG. This shape was provided by a customer who believes the original was created in PowerPoint and then cut/paste into Visio.
Attached is a zip containing a source VSDX, the SVG created by Visio, the SVG created by Aspose Diagram 20.1 (Java) and a sample test class to do the conversion.
We have logged an issue as DIAGRAMJAVA-50683 in our issue tracking system for further investigation. We will look into details of it and keep you posted with the status of its correction. Please be patient and spare us little time.