I am writing inline answers of your questions.
So, from your reply, we assume that this (Autocad 2004) is not working correctly in the current version and this will be fixed in the next version (3.8.0). Is this right?
Yes, GroupDocs.Viewer for .NET 3.7.0 supports rendering of DWG (2004, 2005, 2006), DWG (2010, 2011, 2012), DWG (2013, 2014, 2015, 2016) files. However, some of the files are not getting rendered properly because of some issue in the back end API which is fixed in up coming release (v3.8.0).
Could you also update us what all versions of Autocad will be supported in 3.8.0?
Currently, we are unable to provide you this information. However, if the support of any other version of DWG is added in version 3.8.0, we’ll inform you via this forum thread.
In case of any confusion, please feel free to contact us.