you will face this issue when you used openwrt "DHCP and DNS" to add static leases and when you added static leases in your LAN Page which is available before R69 firmware. we are aware of this incompatibility issue and i agree that it's really annoying when you have duplicate entry which make dnsmasq fail to distribute the ip's.
Please don't use the openwrt "DHCP and DNS" page to add static leases.
Let me clear this thing for you ..
" Call for a comment from the staff on this, I think the progress on static leases has been unacceptable. Earlier versions of the firmware allowed us to add static leases in the NutOS. Then an update caused them to be invisible there, but accessible from the OpenWRT interface. Update again and the option to add them from NutOS disapears, but remains in OpenWRT. Update again and they are no longer visible in Open WRT, but the interface to add them remains. Let me guess, next update will remove the ability to add them from OpenWRT??? "
All our web UI page [ openwrt and NutOS ] is rendering with the help of luci framework which use lua programming language and the config files. At the initial stage LAN Page rendered with the help of Lua. So the was no compatibility issue between the LAN page of ours and "DHCP and DNS" like whatever you added in the any pages will get appear in the other one . But that UI has a lot of issue like getting white page when you add more then 8 static lease, few validation leads were missed . So we developed the custom LAN page which render the page from the config file in different way.
So when you add any static leases in openwrt UI "DHCP and DNS" won't be appear in NutOS UI.
Difference between the config file
From Our UI
config 'host' 'host1'
option 'name' 'joepcfromNutOS'
option 'mac' 'f0:de:f1:5d:e7:33'
option 'ip' '10.10.10.102'
From OPEN WRT UI
config 'host'
option 'name' 'joepc_from_openWRT'
option 'mac' '10:fe:ed:c2:1a:e5'
option 'ip' '10.10.10.104'
As we already have static lease option available in the NutOS, We don't want to leave that static lease option in OPENWRT "DHCP and DNS" which will create lot of headache. So we removed that static leases adding option from "DHCP and DNS" [ openwrt page ]