For my user id, which is 585373512, calling friends_ids(cursor=1483425683211358822, user_id=585373512) returns, among the 5000 ids that it returns, this one in particular:
The id is for a user that was deleted some time ago, but somehow got stuck in my friends_ids list.
For what it’s worth, calling /1.1/friendships/destroy.json?id=308609164 on it to try to remove it doesn’t work either. That returns a ‘Sorry, that page does not exist.’ error.
This bug has existed for months. I patiently was hoping it would get fixed by some back end cleanup, but that appears to not be the case.