Thank you for contacting support. We have tested your VSDM with the latest version 17.5 of Aspose.Diagram for .NET API and managed to replicate the problem of reduced image size. It has been logged under the ticket ID DIAGRAMNET-51266 in our bug tracking system. We have linked your post to this ticket and will keep you informed regarding any available updates. We are sorry for the inconvenience caused.
Thank you for being patient. In reference to the ticket ID DIAGRAMNET-51266, please download and try this latest Hotfix version: Aspose.Diagram for .NET 17.5.1. Please also let us know how that goes on your side.