VNC Viewer/Server 7.12.0 not prompting for logon on one computer (OK for 7.11.x)

I have a Windows 7 and a Windows 10 PC. Each had RealVNC Server and Viewer 7.11.x installed. They were set up so each PC could connect to the other (as well as to Raspberry Pis) with a password being required. I also have Viewer installed on two Android tablets. All the computers are signed in as the same user ID which has a Lite subscription.

I've just updated both Windows PCs to V7.12.0 server and client. I notice that the Win 7 PC (as Viewer) can now access the 10 PC (as Server) without being asked for a password. The converse works OK: the 10 PC is asked for a password to connect to the 7. Also, Real VNC Viewer 4.9.1.60165 on Android is challenged for a password when connecting to both Windows PCs.

Is this a viewer or server problem? I'm not aware of any config changes, and it worked OK until the upgrade, even after I had to migrate from a Home to a Lite subscription.

Does Viewer do any caching of passwords, such that a successful connection (challenged for password) is remembered and a new connection can be made without password being needed until a timeout or a reboot?

I've rebooted the Win 10 computer but not the Win 7 one because it takes ages to shutdown and restart so I normally hibernate the Win 7 PC - the one which is acting as Viewer to connect to the Win 10 as server in this instance.