We were able to reproduce the issue in our environment while using Aspose.Font for .NET 20.12 and following code snippet.
byte fontMemoryData = File.ReadAllBytes(dataDir + "Generic0-Regular.ttf");
Aspose.Font.Sources.FontDefinition fd = new Aspose.Font.Sources.FontDefinition(Aspose.Font.FontType.TTF, new Aspose.Font.Sources.FontFileDefinition("ttf", new Aspose.Font.Sources.ByteContentStreamSource(fontMemoryData)));
Aspose.Font.Ttf.TtfFont ttfFont = Aspose.Font.Font.Open(fd) as Aspose.Font.Ttf.TtfFont;
//Work with data from just loaded TtfFont object
//Save TtfFont to disk
//Output Font file name with full path
string outputFile = dataDir + "Generic0-Regular_out.ttf";
Therefore, we have logged an issue as FONTNET-175 in our issue tracking system for the sake of correction. We will further investigate the reasons behind this issue and let you know as soon as it is fixed. Please give us some time.
We are sorry for the inconvenience.