I am using 1password with the Safari extension and it works perfectly most of the time.
I just have one website where it cannot fill properly the login and password. It seems to fill the password in the username part, and nothing in the password form.
The website (its a stock market website) is:
Can you check this?
1Password Version: 5.4
Extension Version: 4.4.3
OS Version: 10.11.2
Sync Type: dropbox