Hi!
If you switched to fulltext search, then I recommend switching it back. That can cause such issues. The database skips some common words when using fulltext search, and “after” sounds like a very common word. Here is a quick knowledgebase article on this.
Also, here is a post about the different available search logics: Search logics explained
Plus make sure you have the search cache disabled. That can give you different results when you add new products.