I tried with the same browser language preferences as you but still don't reproduce the problem. The browser language preference is used only when there is no cookie present (and only if you check the relevant option in Polylang settings).
Just to be sure that we test the same thing. Your problem is when you click on the "English" item. Not when you type the url http://misvblog.com in the address bar (in that case it is intentional that you come back to the last browsed language: Polylang uses referrer detection to differentiate the the two cases).
How do you clear the cookie? Do you delete only one or all?
