When ODMAD is migrating users from AD to AD, it's creating them with the default password and users are being asked to change it immediately.
Password sync is either not configured or not working properly
Such behavior is by design. Default template password is being applied during the AD user's creation and default template mapping sets pwdLastSet to 0, which forces user to change password at the next logon.
Usually it's not a problem is password sync is configured properly and functioning, as it'll update the newly created user's password almost immediately. Please review if password sync is working properly.
Important note: this is true only for modern or legacy password sync mechanisms. Password Propagation Service (PPS) is only triggered by user, actively changing the password in the source. If PPS is configured, then users must either actively change their passwords in the source domain, or login into the target using default password and changing it as requested during the logon.
