Execute only action_default_ask_rephrase in Two Stage Fallback Plicy

No problem. Try to call a method from your custom fallback to check if the user is in a second fallback (consecutive or not). In your method, place something like:

for event in reversed(tracker.events[:-1]):
    
    if event.get('event') == 'action' and event.get('name') == 'action_custom_fallback':                  
        return True

return False