At what point are you seeing this? Only at the initial array start or on all subsequent scans?
I had some time and dug into this a little more. I saw in the code that it's running a ping check against github.com which is indeed failing from my unRAID machine. It does not fail from other systems on my network though and my unRAID box is still able to connect to github.com, just not over ICMP.
root@mnemos:~/usr/local/emhttp/plugins/fix.common.problems# ping -c 2 github.com
PING github.com (18.194.104.89) 56(84) bytes of data.
--- github.com ping statistics ---
2 packets transmitted, 0 received, 100% packet loss, time 1005ms
root@mnemos:~/usr/local/emhttp/plugins/fix.common.problems# telnet github.com 80
Trying 18.194.104.89...
Connected to github.com.
Escape character is '^]'.
^]
telnet> quit
Connection closed.
root@mnemos:~/usr/local/emhttp/plugins/fix.common.problems#
I don't see anything in iptables that would be blocking this(though I'm not the best with iptables so I could be missing something), and I am able to ping other public sites such as google and yahoo from the unraid host.