The problem is most likely related to caching.
Some users report duplicate content appearing on their sites. Or they see new content on the source site but fail to insert that content into their site and the campaign does not recognize the new articles. Upon investigation, we soon see that the problem is emerging from a caching plugin. Whether it’s the site itself, which is easier to fix, or more difficult, there is caching in the source feed.
Why might RSS feeds present problems with caching plugins?
Caching plugins, and sometimes the cache on the host server, have no way of detecting and clearing the cache to update dynamically. Therefore, site content, such as an RSS feed, is not updated properly by maintaining old content until the time the cache is refreshed. There are times when these same poorly cached feeds present duplicate items giving the impression that they are duplicated by the campaigns in the target WordPress.
What can I do?
If the cache is on your site:
You need to empty the cache files to avoid duplicate feed items or to have the feed items updated on the front of your site.
Many good cache plugins have options to turn off the cache on feeds or clear the cache to update it each time content is inserted into the site.
If the theme or plugin you’ve installed doesn’t delete the cache automatically, we recommend that you contact their developers and ask them if it supports dynamic content.
If the cache is on the source site:
Well, this is a bit difficult, since it doesn’t depend on the WPeMatico or the site that hosts it, so you just have to try different options to get the best result.
Some recommendations (only for these cache problems):
If you know what time the cache is updated on the source site, and they always update at the same time, you can schedule the campaigns to run just after that time. Like being 10 minutes later.
You can deactivate in the duplicates control, only for that campaign, the checking by hash and leave only the duplicates checking by titles.
You can set the campaign to fetch only once a day or a couple of days to be sure that the cache was refreshed.
But the best option would be to contact and ask the owner of the source site for a better cache with their feeds because they are not refreshed according to the site.