Sorry for the inconvenience. Please spare us some time to further investigate this behavior.
This issue is reproduced using .NET framework projects only. In .NET60 or .NET70, folders are created but are blank. We will continue investigation and let you know once we have the fix available.
A post was split to a new topic: Persistent CustomTempFonts Folder Growth Issue in GroupDocs.Viewer 24.6.0 and 24.9.0 for .NET Framework