If you are referring to problems I encounter on userswp.io, then I’ve attached what I get when I login via FB from this exact page (topic).
When I do the same from the Home page of your website however, it lets me in via FB no problem.
As far as I remember I’ve seen the similar problem when logging in via Google, but I cannot replicate it right now, so maybe I remembered it wrong, not sure, If I encounter smth similar with Google, I’ll let you know.
In regards to my website, I’ll see if the login/register pages are added to the no-cache list. Thank you.