I flashed a spare DIR-615 D4 set up as a router from build r20453 and without erasing any existing settings. It seems to be working fine with WAN connection set up as DHCP. Port forwarding is working.
The usual startup command fix to enable both radios is no longer required too.
On one occasion after editing some settings, the GUI failed to reload. I could ping the router and router was routing traffic. It also failed to load when another computer was tried. Rebooting the router fixed the GUI issue.
