Summary:The workflow status column sometimes doesn't show a URL, but everything to do with the workflow progress seems to be fine. It seems this may be happening because the URLs are longer than 255 characters, which is a SharePoint limit. Is there any way around this?
Product:All Workflow for SharePoint on-premises
Regarding the 255 character URL limit on the workflow status column: we cannot influence this hard limit imposed by SharePoint. There is a lot of information on the web about this hard limit, for example, you could refer to: http://social.msdn.microsoft.com/Forums/eu/sharepointdevelopment/thread/8a709ec8-b174-4073-9573-7d3fd0135c76 or http://stackoverflow.com/questions/341350/adjust-sharepoint-url-field-length. Because we cannot influence this, the only options are for you to contact Microsoft in the hope you may be able to influence them to change it (which frankly is highly unlikely) or work around it by shortening the URL of the sites/subsites/lists/folders.