Double posts and some are skipped

Hello

I’m trying to work with your plugin and so far so good
The only thing that doesn’t work fine is when I import a csv file with new products no all products are posted on facebook and some are posted more than one time.

You can check here:

new products: https://www.onesite.nl/latest-postcards/
facebook: https://www.facebook.com/postcards4saleNL/

please help. thanks in advance

The page I need help with: [log in to see the link]