Dose not prevent duplicate posts anymore

Hello,
I am using Cybersyn for more than one year. It was working well but recently it retrieves duplicate posts frequently and it causes duplicate posts on my site. I think “feed duplication control” is not working properly anymore(at least on my site). I don’t know whether other users have encountered this problem but I even installed several post duplicate checker and post titles duplicate checker plugins. Those plugins prevent from posting duplicate titles as WP regular posts. However, the plugins can not prevent duplicate posts created by Cybersyn!
I need your help.