We are encountering an issue with Slides where some user provided HTML contains duplicate style attributes - looks like this causes an exception in Aspose.Slides shape.AddFromHtml method. Example c# code below:
using Aspose.Slides;
using HtmlAgilityPack;
var presentation = new Presentation();
var slide = presentation.Slides.AddEmptySlide(presentation.LayoutSlides.FirstOrDefault());
var group = slide.Shapes.AddGroupShape();
var newShape = group.Shapes.AddAutoShape(ShapeType.Rectangle, 0, 0, group.Width, 0);
string html = "<p style=\"box-sizing: content-box; box-sizing: content-box\">Some text</p>";
newShape.TextFrame.Paragraphs.AddFromHtml(html, null, "");