@cmb:
That log just looks like they got click happy on the submit button of the portal page and submitted it multiple times. No harm in that, but it will show as multiple logins since it is.
The "No valid RADIUS responses received" is what it says - your RADIUS server didn't respond.
Thanks you
About No valid RADIUS responses received, my RADIUS respond but this message appear whenever subscriber login fail (wrong password, wrong username, …) only one time fail, this message appear and must wait about 20s to login normally again.