I'm using 'Copy to SharePoint' workflow action to copy a video file between two site collections using Nintex workflow. For some reason that does not work perfectly well in all cases.
Looking at the video file structure in SharePoint, once video is uploaded a new document set is created for it containing the video file itself plus a thumbnail. Once 'Copy to SharePoint' is completed the actual video file is copied across, however that is not the case for the original thumbnail image. There is no new thumbnail generated either.
Issue was solved with upgrading Nintex 2013 Workflow 3.1.2.0 to 3.1.4.11 Not mentioned in the release notes though.