In order to ensure proper functionality, I would recommend expanding any nested echo media player group created by this blueprint in a template when calling the notify.alexa_media service. For example:
action: notify.alexa_media
data:
message: this is a test
target: "{{ expand('group.all_room_occupancy_echos') | map(attribute='entity_id') | list }}"
data:
type: announce
method: all