When creating a site collection based on the team site or document centre the feature ‘ReviewRouting’ is not enabled (yet). This results in ‘unknown task type’ in the error logs and 'Error Occurred' in the workflow status screen.
To fix this:
Enable the standard SharePoint feature ReviewRouting: Id = 02464C6A-9D07-4F30-BA04-E9035CF54392
Kudo’s to Stef for finding this.