I'm so sorry for not getting back to you sooner. I just got into the admin area of your site to investigate more. I don't see any reason that the content from the category you PM'd me about should be auto-posting.
Can you confirm that it still is autoposting? I went to the JFBConnect -> Channels -> History area. In there, on page 6, item #120, I see an article from that category did autopost back in June. However, since then, I don't see any other records of an article in that category posting. In the Joomla Article manager, the last article published to that category was 2018-06-08. Since then, there's been no new content and there's no record in the Channel History of even a test article being posted (if you created a test article in that category and deleted it, I believe it would still show in the History tab).
So, for now, I can't see any reason it would autopost. If you can give me some steps on what you're doing and how best I can test, I'll gladly investigate further. I don't want to start autoposting content to your feed though without you being aware it may happen. It's definitely baffling that you said you disabled 'everything' and it still autoposted. If you could explain what you disabled, that may help understand as well.
Again, sorry for the delay, but we'll gladly help investigate however we can once we understand how to test more.
Thanks,
Alex