Greeter no longer accepts my user password, although it is correct

## What Happened
Decrypting the hard disk works without errors, and via tty I can see that the keyboard works as well. Using the keyboard with another live Linux USB also works without problems.
Unfortunately, the user password is no longer accepted. The password input field shows again and again only the animation for entering an incorrect password. tty thinks for a while and then shows again only the prompt.
The issue occurs for me only recently. However, I did not change anything in my password in the meantime.
I am currently using an external USB keyboard on a laptop.
The issue is critical for me because I can no longer log on to my system and use it.

## Platform Information
I use an updated and stable version of elementary OS Hera.