Login Credentials Are Invalidated Intermittently

Since i upgraded to v12.8.0, i noticed that user logins are intermittently invalidated. When users request for password reset and supply the same password, it gets accepted by the system and users can login and perform their normal functions. However, sometimes within 24 hours, same password is returned as invalid by the system again and the cycle has to be repeated with user requesting for password reset and supplying same password.

To test, i asked a couple of users to use different and more complex passwords on password reset but the same issue reoccurs nevertheless. Can someone look at this issue and try to resolve it?