Unable to save “excluded” blog posts

I search for January, I select the blog posts that I want to exclude and click the exclude button at the bottom. After that, I search for the word “February”, select the blog posts I want to exclude, click the button “exclude” at the bottom. My previous selected blog posts to exclude are no longer excluded. his happens to every new term I search and try to exclude.

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