"Minimum number of password before reuse" is set to 6.
User will change password 6 times so the password history will have following 6 passwords history.
When users try to change password again in reverse order (ex. attempt change password to pass5 --> pass4 --> pass3 --> pass2 --> pass1 to see how many passwords in the history will be rejected) and users will be able to change to pass3 although 6 passwords in the history should be rejected.
When a new password policy with same setting is created, that works as expected.
Release : 12.8.x
This password policy was created long ago and lacks several elements in its object structure.
Delete and recreate the Password Policy to ensure the Password Policy has all the required elements.