I have struggled with a bug using LinkedIn's OAuth 2 authentication.
Every time I was trying to "login with LinkedIn" to my site, only via mobile, I would get the authorization server encountered an unexpected condition.
Bummer.
It took me quite a while to figure out the problem. Apparently my mobile keyboard adds an extra "space" character after my email address. [email protected]_.
It does not trim the email string, and it does not return an "email and password does not match" error, rather redirects to the callback address with the said error.
This is reproducible in mobile and desktop too.
I couldn't find a proper place to report bugs to LinkedIn.