UI Action button not showing in certain workspaces

[JAmos]

I have a scoped application published to the ServiceNow Store and a customer has reported some behavior I've been unable to reproduce in any of my environments (PDIs and vendor instances) or to successfully diagnose in theirs.

As the title indicates, the issue is with a UI Action button that, for them, is not showing in one a workspace view.  I've created a simplified example of the button (all settings match, it just doesn't have the real script code and uses two global roles).  

The button targets the 'Task [task]' table and in the customer environment DOES SHOW in the following instances:

• Any record that is a sub-type of Task when viewed in standard UI
• The above includes Case records which are provided as part of the Customer Service Management (CSM) plugin (com.sn_customerservice)
• Any record that is a sub-type of Task EXCEPT Case when viewed in the CSM/FSM Configurable Workspace

Naturally it's that last item that is the kicker as this customer utilizes this particular workspace and Case records for much of their workflow.  We even tried updating the 'Table' field on the UI Action button to specifically target 'Case [sn_customerservice_case]', but with no effect on the behavior ... button still doesn't show on Case records in this workspace.

So the question is: What would case a UI Action to behave this way?  Is there something that, perhaps, should be getting created that isn't in their environment or ... ?

Attached are some screenshots of my sample version of the button so you can review the exact values for the basic configuration settings.