Openwrt gives lan interface same IPv6 address as 6rd interface

I have just set up OpenWRT with a very typical 6rd configuration, I just put the relay address, prefix and prefix length, and it did the rest, but I'm having issues with time outs on new or idle TCP connections.

Notice in the screenshot that the IPv6 address on 6rd interface is same as my lan...

This is what openwrt automatically assigned... is this correct? I'm not sure it is, I see a dnsmasq "Address in use" error when I restart the interface

https://forum.openwrt.org/uploads/default/original/3X/a/b/abba38d1a8147b95335daf30220423071965f649.png