Admin Access Lockout Risk when upgrading or downgrading from versions with PBKDF2 support
PBKDF2-based password hashing is supported starting in versions 7.2.11, 7.4.8, and 7.6.1. If a device is upgraded to one of these versions and administrator credentials are saved, then later upgraded or downgraded to a release prior to PBKDF2 support (for example, upgrading from 7.2.11 to 7.4.7), the admin login will fail, resulting in administrator access lockout.
Before upgrading or downgrading, make sure that the login-lockout-upon-downgrade command is disabled:
config system password-policy
set login-lockout-upon-downgrade disable
end