I noticed that modifying the log settings does not take effect.
I went and added a remote log server, I also modified the default buffer from 16 to 32, but did not receive any logs.
So I logged in through ssh and went and had a look and saw that the syslogd process was still using the old settings.
I suppose the GUI should either restart the service with the new settings or at least tell you that you need to reboot the router.
Although a reboot is a bit over the top for such a change, it should be enough to restart the service.