We have the same versions, 1.6.7206.42072 (found on ? on portal) is the same as 15.0.1102.597 (RS isntance). We also have the same Desktop version.
Do you use Iframes ?
If you go on the portal, on a specific report and add the ?rs:embed=true to the url, does it still redirects to favorites ?
Also if you do network debugging (F12 on most of browsers, network pane), do you see any attempt to reach the report url ?