Intro
This has happened to me on two different laptops so maybe it’s a thing. I type in the known, correct password to unlock it and it comes back with invalid password or something similar.
Then I finally figured out what was happening when I observed more carefully.
The solution
I typed in the characters of the password one-by-one and watched the password screen:
···
Then I typed in the fourth character and … nothing! No · was echoed back to the Password field! No wonder it thought I was typing in the wrong password. Technically, from its viewpoint I was. So I typed the fourth character harder until it finally responded by echoing a ·, and proceeded with the rest of the characters which went more smoothly. Then the laptop unlocked.
I think the two laptops actually suffer from two different problems. The one may have a sticky key that doesn’t always press correctly – a key that I use as part of my password. The other laptop is just bogged down by a lot of bloatware, to the point where it is so slow it doesn’t echo characters back to the screen as fast as I type them in. I learned to repeat the missed character or even re-type it to make it take. Hard to believe but it’s true.
Conclusion
The mystery of the correctly typed password not unlocking the laptop screen has been resolved. Character echo was not occurring correctly, necessitating repeating keys while looking at the results on screen.