Does not possible to shutdown accel-ppp via accel-cmd shutdown command, because systems service has method Restart=always
Propose to change it to on-failure

If set to on-failure, the service will be restarted when the process exits with a non-zero exit code, is terminated by a signal (including on core dump, but excluding the aforementioned four signals), when an operation (such as service reload) times out, and when the configured watchdog timeout is triggered.