I believe you're right on target, as usual! Time permitting,  educate me a little (or a LOT), please...

I didn't understand what I was seeing with the ps ax | grep MMDVM command.

root@WB5NFC-2186:/opt/MMDVM_Bridge#  ps ax | grep MMDVM
  668 ?        Ss     0:01 /opt/MMDVM_Bridge/MMDVM_Bridge /opt/MMDVM_Bridge/MMDVM_Bridge.ini
 1265 pts/0    S+     0:00 grep MMDVM

So I ran systemctl status mmdvm_bridge

● mmdvm_bridge.service - MMDVM_Bridge Service
   Loaded: loaded (/lib/systemd/system/mmdvm_bridge.service; enabled; vendor preset: enabled
   Active: active (running) since Wed 2019-07-24 13:51:14 CDT; 34min ago
 Main PID: 661 (MMDVM_Bridge)
   CGroup: /system.slice/mmdvm_bridge.service
           └─661 /opt/MMDVM_Bridge/MMDVM_Bridge /opt/MMDVM_Bridge/MMDVM_Bridge.ini

Which I think... tells me, yes dummy, it's already running and there's your problem.  How I started it at boot and now how I keep it from starting at every boot (while testing) are questions I can't answer.....