I have the same issue with my site as well. It seems to be intermittent but it fails more so than not. If I click to log in it will open the popup and load my site inside the popup. This is the same result for both Facebook and Twitter and for both registration and login.
For your question on redirection, I’ve tried both Same page where user logged in and Homepage and the same bug happens.
My site url is https://isitfunnyoroffensive.com
Any help is greatly appreciated!
