@r-a-y: so i tested with a local environment. strange thing: the membership requests now work fine from the group page, but not from the directory page (no notification sent, 404 loading on start page WITHIN the frame for the respective group).
thanks for replying so quickly. highly appreciated!
@r-a-y: activity streams are off, site tracking and notifications are on. didn’t have any problems with these settings until wp 4.0 and bp 2.0.
@danp: plugins deactivated, same story, sadly. and, as far as i can see, no other errors concerning messages. the site runs on the “generate press” theme in the pro version.