It ought to work, we had similar issues which were caused by .tiff images which were in the .docx file. We converted those to .png first, did the render and hey presto. Everything was fine.
Please try the latest version of Aspose.Words for .NET 19.4. If you still face problem, please ZIP and attach your input and output documents here for testing. We will investigate the issue and provide you more information on it.
If Aspose.Words for .NET Standard is intended to be used in Linux environment, an additional NuGet package should be referenced to make it work correctly with graphics: SkiaSharp.NativeAssets.Linux for Ubuntu (it also should work on most Debian-based Linux distributions) or Goelze.SkiaSharp.NativeAssets.AlpineLinux for Alpine Linux.
We always appreciate positive feedback from our customers. We suggest you please read the following article. Hope this helps you. How to Run Aspose.Words Docker