Following my previous report, #223618, I could see that you made a change to the site which https://demo.weblate.org/accounts/password/ says
>Your password can't be too similar to your other personal information. >Your password must contain at least 6 characters. >Your password can't be a commonly used password. >Your password can't be entirely numeric. >Your password can't consist of single character or whitespace only.
I found that it is possible to create a password with a single character