OpenWRT and NAMED or BIND
...here's a quick painful one;
If you choose to upgrade your NAMED / BIND Server, it's not enough to just upgrade with this command: opkg update bind-server (or via the LuCI GUI)
You also have to update every other package, via OPKG or the LuCI GUI that is installed and even mentions the term "bind" to make things work properly. Oh, not done yet.
...and don't forget opkg upgrade libuv OR opkg upgrade libuv1 (or via the LuCI GUI), otherwise a weird "uv_udp_init_ex" error may occur.
So in the end OpenWRT has made it possible to upgrade the NAMED / BIND server package (bind-server) and not automatically update any dependencies as part of the process, which happen to be a requirement. Woof!