Multiple NOTIFY is ignored

Hi,

I've a question to the pgsql NOTIFY feature...

I use something like

SELECT dblink_connect('{0}', '{1}'); SELECT dblink('{2}', '{3}'); SELECT 
dblink_disconnect('{4}');
where {3} is
NOTIFY upd_pgm, '0|UPDATE|A|'

SELECT dblink_connect('{0}', '{1}'); SELECT dblink('{2}', '{3}'); SELECT 
dblink_disconnect('{4}');
where {3} is
NOTIFY upd_pgm, '0|DELETE|A|'

This works. Both notify are recognized.

If I only do one
SELECT dblink_connect('{0}', '{1}'); SELECT dblink('{2}', '{3}'); SELECT 
dblink_disconnect('{4}');
where {3} is
NOTIFY upd_pgm, '0|UPDATE|A|'; NOTIFY upd_pgm, '0|DELETE|A|'

only the notify with UPDATE is recognized.

For further explanation... the working solution uses separate dblink 
connections and calls for each notify.
Where as the not working tries to use only one dblink connection and 
call.

As far as I can read from the documentation...
"If the same channel name is signaled multiple times from the same 
transaction with identical payload strings, the database server can 
decide to deliver a single notification only. On the other hand, 
notifications with distinct payload strings will always be delivered as 
distinct notifications." 
(https://www.postgresql.org/docs/current/static/sql-notify.html)

Here the channel name is identical, but the payload differs with 
UPDATE/DELETE.

So why the 2nd notify is not delivered/recognized?

Thanks
Markus