Howdy,
Seeing the same thing when trying to config IPv4 manually when coming off DHCP via wifi with a new Amp running 5.0.537347 and latest IOS.
1) Can only configure the IP address (IOS)... really need to be able to configure subnet mask and gateway (as well as DNS). There are many reasons why you want these fields configurable and NOT self-guessing and locked.
2) The subnet field is locked with a 255.255.255.255 subnet mask. I can connect via IOS via wifi (at least I think it's connecting via wifi and not BT).... Have not been successful yet with Airplay 2 yet (albeit airplay sees the Amp).
3) The gateway field is also locked... which will cause the AMP to not connect in multi-vlan environments.
4) Really need the DNS server field(s) configurable as well please.