Hi Emiliano,
Ok, that's a situation that I already found in the past. You have configured the wrong Logout URL, ie, that logout URL it's not for saml (probably its for ws-fed protocol), and it seems to ignore the attached saml message, but will try to logout the client, in this case with saml, and that's why you see 3 log entries. If your adsf supports logout inititiated by the SP with saml, then you just need to set the right logout URL for saml, otherwhise you should not logout from your applications through the IdP component. Would say to just redirect the browser to that URL directly from your apps.
Regards.