Resolution:
1. To stop a specific RTserver, use this syntax at a minimum:
        rtserver -stop -server_names &ltlcn of RTserver>

2. To stop the first RTserver set by the SERVER_NAMES option, use one of the following:
   a. rtserver -stop -command <.cm file for RTserver>
   b. rtserver -stop  /* where the default rtserver.cm file(s) will be referenced */
Note that predicting which RTserver will be stopped can be tricky using method 2b.

The rtserver.cm files will be read in this order:
$RTHOME/default/rtserver.cm
$HOME/rtserver.cm,
$PWD/rtserver.cm.

So, SERVER_NAMES options may be set in multiple .cm files; and, the last read SERVER_NAMES option would override earlier read values.