Windows 10 Lock Screen: No Keyboard

I upgraded my Surface Pro 3 from Windows 8.1 to Windows 10 via ISO on the launch date and noticed a strange behaviour when using it without the physical keyboard attached. When I boot or lock the device and it enters the lock screen, tapping the PIN (or password) field should trigger the special on-screen keyboard for me to enter the PIN/password, but it doesn't. I have to go through the accessibility menu on the bottom-right to trigger the generic on-screen keyboard in order to type in my PIN/password. This generic keyboard is obviously not fit-for-purpose so I'm hoping someone has a clue here on what's wrong.

Update 2

This tip seems to have helped somewhat.

Go to Settings > Devices > Typing

Enable the option Automatically show the touch keyboard in windowed apps when there's no keyboard attached to your device.

I will test this further and mark this as an answer if this proves to solve the problem.

http://www.windowscentral.com/auto-display-touch-keyboard-windows-10-desktop-mode

Update 1

This still happens intermittently, though during the first login after the update was installed, the correct on-screen keyboard managed to pop up.

This got resolved in the August 11th cumulative update. Not sure why either.