Thanks for your inquiry. In case you are using an older version of Aspose.Words, I would suggest you please upgrade to the latest version (v13.1.0) from here and let us know how it goes on your side.
I have tested the scenario by using a web URL and have not found any issue with description content control and Image control of output document. I have attached the output Docx file with this post for your kind reference.
If you still face problem, please use the following configuration settings in your application. Hope this helps you. Please let us know if you have any more queries.
<httpWebRequest useUnsafeHeaderParsing="true" />
HttpWebRequestElement webRequestSettings = new HttpWebRequestElement();
webRequestSettings.UseUnsafeHeaderParsing = true;