This issue occurs in scenarios where you have a BrightWork web part with a ribbon (e.g. a Board, Reporter, Chart, etc.) on a web part page that also includes a List View web part.
The List View web part shows items in groupings. However, if you then expand a grouping, navigating away to another page, and navigate back to the web part page again, these steps can result in the List View web part hanging with a 'Working on it...' message.
This is caused by an issue with the SharePoint ribbon file (sp.ribbon.js) which is included in SharePoint. BrightWork is not in a position to provide a direct fix.
Workarounds you could consider include: