Why my keychain is not showing saved password?

I have a password for file saved in my keychain. There is some bug preventing me from seeing it. After clicking 'show password' and entering the right password to 'login' keychain the window flickers but the password is not shown. I can't copy the password. I know that I am entering the right password because there is an error when I enter wrong password. I can't lock the 'login' keychain, I can't change the password to it. Basically I can do nothing about that. How is this functionality working at all? How to get to my saved password?