Re: Redirecting Login
I was seeing something similar and I found it relates to ADMIN_COOKIE_PATH in wp, and $bb->wp_admin_cookie_path in bbPress.
In my case, I had bbPress located at domain.tld/forum/ for a wp install at domain.tld. If I set the wp ADMIN_COOKIE_PATH to /wp-admin/ as usual, then I got this behavior… but if instead I set it to “/” then things work fine.
This may or may not be related to the issue you are seeing.