An example feed is http://export.arxiv.org/rss/cs.

The problem is that body parts of multiple closed (unfolded) articles still appear and I cannot close such articles. Strangely, this feed passes RSS validation: https://validator.w3.org/feed/check.cgi?url=http%3A%2F%2Fexport.arxiv.org%2Frss%2Fcs

You can check the problem via https://songsong.postech.ac.kr/FreshRSS/i/?get=f_33 without login (or via your own FreshRSS.)