I have my Linux machine configured to automatically login to my user account, and of course lock the screen immediately afterward. During login, the password field of the lock screen loses focus several times (becomes deselected). Not only does this force you to use your mouse before you can type the password, but typing it will itself get interrupted sometimes.

Reproducible: Always

Steps to Reproduce:
Set your system to auto-login to your user account. Make sure you have a few programs configured to auto-start as well.

Actual Results:  
Early during login, the field in which you type your password to unlock the screen will get deselected.

Expected Results:  
The password field should remain active, and not lose focus due to other events.

I imagine the cause is that programs which are set to auto-start are stealing focus, even if we can't see them from the lock screen.