According to Ruddigkeit.net, if you have “password checking” enabled or use a password policy in Domino, Lotus Notes remembers the last 50 passwords you used to protect the Notes ID file.  If you try to use one of these passwords you will get the error “You have used this password before.  Please choose a new one.”

But in Lotus Notes 8.0.2 there is a reproducible bug with this function, as you will always get the message, “Your password change succeeded!”  By not receiving the message that the password was changed or already used, it can confuse a user who tries to log in the following day.

But, it appears as if the bug is fixed in version 8.5.