Guys I have having this issues for quite sometime. But I haven't been able to find a solution to it. Whenever I make a change in LuCI GUI and click "Save and Apply", it doesnt saves the changes. Be it Wifi password or setting up DHCP leases. Although I have been able to change the Wifi password using Putty/SSH console. This shows that there is some kind of problem with LuCi. I dont know how to configure manual DHCP leases in SSH. If anyone knows about this issue I would be grateful for your support. below is my config details
TP-link WR841ND v7.2
OpenWrt Barrier Breaker 14.07 / LuCI Trunk (0.12+svn-r10530)
Note: I have installed Dynamic DNS and SQM QOS tools. I hope that is not the issue as they are and have been working correctly.