Why PostgreSQL's service are different between system service and pg_ctl?
If you start the server manually using pg_ctl, systemd doesn't know about it.

It will happily try to start the server, which will fail (because the server is already running), and it cannot stop the server, because it does not know it is running.

So always use systemctl when starting and stopping the service. Reloading with pg_ctl reload is fine.