Weird login behaviour.

omits wrote:

This could be construed as a bug. If my laptop is showing the logon screen (blank entry box). I decide to clean the keyboard and of course gobbledegook gets entered as the cloth runs the keyboard.

However if I press return and wait for the refusal and then type in the correct password is repeatedly gets refused. I have to turn the power off and restart (maybe just restart, haven't tried that; same thing though) and start with a 'clean' entry box. I do power off sometimes but I think it starts up again when I lift the lid. Point is if the entry box is clear when typing the correct password it should be accepted.

Try locking the screen before cleaning...Control Command Q

You would not want to use the Return key to clear(?) the psswd, —use the backspace/delete key to remove/clear the entry.

Macs with TouchID is an option for unlocking

omits wrote:

Ah! yes lock the screen. Thanks. However, whether the entry box is selected (all) or clear the anomaly occurs. So if an empty entry box means the correct password has to be accepted and it is refused then it is a bug, albeit probably not an important one as long as the user thinks to restart if it happens to them. In my case entering numerous keystrokes probably caused some sort of overrun leaving characters in the buffer to be analysed as the entered password. Whatever I guess.

Choose Apple menu  > System Settings (or System Preferences), click Touch ID & Password, then turn on the setting to use Touch ID to unlock your Mac.

If Touch ID isn't working on your Mac - Apple Support

To be proactive you can file a bug report /submit your Apple Feedback here:  http://www.apple.com/feedback