I set the LAN to 10.30.4.2 and it gave out a DHCP of the same address - not fun!

This is not a bug, this is a setup issue. You must reconfigure the DHCP pool so the pool of addresses do not conflict with the LAN IP address that you are trying to assign.

Go into the DHCP server setup and reconfigure the DHCP Pool so it does not conflict with your LAN address