When I open your workbook, and click the link for "testing group" in the Coffee Chain data source, it is working properly. However, I am not on the latest release. Have you contacted Tableau Support? firstname.lastname@example.org
Yes, after talking with Tableau support it seems that this was an issue introduced somewhere between 8.0.0 and 8.0.4.
I rolled back both Desktop and Server to 8.0.0, and everything works properly again.
Tableau has indicated they are planning to fix this in 8.1 at the latest, hopefully in a maintenance release before then.