Reset symlinks of unit files
When a systemd unit file changes on disk, only
systemctl daemon-reload is run. Systemd will then consider all the new attributes, that are set in the unit file, except for attributes of the '[Install]' section, which require a change of the symlinks that are created when the unit is first enabled.
This should be fixed by running
systemctl reenable unit.type whenever the
[Install] section of the unit changes.