PubMed search oddity: many misses on Title when thorough

I have noticed a great deal of searches on Pubmed using “title” search terms come up with “No results found” when sequential words from the articles title are correctly entered in the search box.  However, if you try different sequential words from that same title it will magically all of a sudden find it.  Often the most unique sequential words from a given title turn up no results but more vague words from same title meets with success.  Kind of odd.