For those who has problem with turris 1.x can you please try this workaround if it works for you? I tried to reproduce DNS problem and only got some errors regarding unbound package and after this workaround problem disappeared.
echo "nameserver 1.1.1.1" >> /etc/resolv.conf
rm -rf /etc/unbound
opkg update
opkg install --force-reinstall unbound
reboot
After reboot my turris 1.x started behave normally.
Please let me know if it works for you or not. Thx.