Crating a thumbnail of the attached PPTX document yields improper rendering.
const float scale = 300 / 96f;
using (var ppt = new Presentation(@"ConversionIssue.pptx"))
{
ppt.Slides[0].GetThumbnail(scale, scale).Save(@"ConversionIssue.pptx.jpg");
}
ConversionIssue.zip (340.2 KB)