Is there a bug reporting facility?
I was having a bit of trouble getting DNS to work and when logged in to the web gui noticed a red dot and message saying DNS was not running. Logged in to the CLI and ran sudo service dnsmasq status, this was the output:
pi@raspberrypi:~ $ sudo service dnsmasq status
● dnsmasq.service - dnsmasq - A lightweight DHCP and caching DNS server
Loaded: loaded (/lib/systemd/system/dnsmasq.service; enabled)
Drop-In: /run/systemd/generator/dnsmasq.service.d
└─50-dnsmasq-$named.conf, 50-insserv.conf-$named.conf
Active: failed (Result: exit-code) since Fri 2017-06-23 23:12:14 UTC; 3min 5s ago
Process: 1589 ExecStartPre=/usr/sbin/dnsmasq --test (code=exited, status=1/FAILURE)
Jun 23 23:12:14 raspberrypi dnsmasq[1589]: dnsmasq: bad address at line 2 of /etc/dnsmasq.d/03-pihole-wildcard.conf
Jun 23 23:12:14 raspberrypi systemd[1]: dnsmasq.service: control process exited, code=exited status=1
Jun 23 23:12:14 raspberrypi systemd[1]: Failed to start dnsmasq - A lightweight DHCP and caching DNS server.
Jun 23 23:12:14 raspberrypi systemd[1]: Unit dnsmasq.service entered failed state.
Jun 23 23:15:18 raspberrypi systemd[1]: Stopped dnsmasq - A lightweight DHCP and caching DNS server.
Noticed the error so checked the file and found:
pi@raspberrypi:~ $ cat /etc/dnsmasq.d/03-pihole-wildcard.conf
address=/www.thesun.co.uk/192.168.1.14
address=/www.thesun.co.uk/fd18:d276:cf2c:3500:f8d2:271f:8af8:a5f4/64
Turns out a URL I tried to blacklist I wildcarded instead and it didn't like the IPv6 entry for it. Removed it from the blacklist and been working fine since.
I can try to recreate the problem and send logs if required.