"Stop post queue queuename" does not work (4330232)

When attempting to stop a named Post process, the process does not stop although the sp_ctrl prompt returns without any error.

1. The qstatus shows the name of the Post queue which in this case is QUEUE1:

sp_ctrl (server_name:port_num)> qstatus

Queues Statistics for server_name
  Name:  QUEUE1 (o.source_SID-o.target_SID) (MTPost queue)
    Number of messages:          0 (Age         0 min; Size          0 mb)
    Backlog (messages):          0 (Age         0 min)

2. The command to stop the named post queue is issued:
sp_ctrl (server_name:port_num)> stop post queue queue1

3. However, the Post process is still running.