Why does our user keep getting locked?

Summary:

One of our users keeps getting locked. We changed the login thinking that would prevent people from locking it with old credentials but it happened again.
"Password Expires After" is set to 999 Days and it is happening more often than that. Is there anything else that can lock a user other than someone trying to log in with the correct username and incorrect password? Is there any way to get a log with dates and IP addresses or something for when someone tries to log in with an incorrect password?

We made SR 3-36689481591 to ask Oracle to tell us more about the login attempts that were locking it and they said to ask here.