Filesystems like /hedvig/d13 are not discovered with df check but with mount check

Ah, sorry, misread the previous post. So over the network there’s an issue. Which explains why you’re not seeing your results in CheckMK. Ok, so let’s check if there may be a permission issue after all. First, let’s see if xinetd is running with the proper permissions:
ps axuwww | grep xinetd

Should return something like this:
root 1488 0.0 0.2 49972 4560 ? Ss 09:34 0:00 /usr/sbin/xinetd -stayalive -dontfork

Then the contents of /etc/xinetd.d/check_mk, should read something like this:

service check_mk
{
        type           = UNLISTED
        port           = 6556
        socket_type    = stream
        protocol       = tcp
        wait           = no
        user           = root
        server         = /usr/bin/check_mk_agent

        disable        = no
}

I’ve stripped out comments and options that are not active.

Also, I noticed that you’re still using an old version of the agent: 2.1.0p1, while 2.1.0p16 is available. It’s a long shot but you could try upgrading it.