macOS Sierra doesn't automatically authorise network-mapped folders on login?

Having upgraded from El Capitan I've always had mapped network share folders log in automatically (mapping NAS drives to connect to on startup, using System Preferences > Users & Groups > Login Items).

However with macOS Sierra I'm now needing to manually confirm my log in & password for the NAS every time I boot up. Keychain does remember the login information, but it only appears pre-filled, and the network locations aren't automatically mounted on start-up. Every time I boot the machine, I am presented with a "Connect" dialogue with pre-filled passwords. Previously this would all happen automatically with no need to manually intervene with a click to connect for the process to proceed & map the folders.

Does anyone know a way for this to change back to just running automatically as in OSX previously? It is happening on both Macs I have upgraded & hoping there is a setting I can change for this to work.

Thanks in advance.