Why it matters
The words a page repeats most are what it is about, as far as a reader skimming it can tell. When those words do not appear in the title and the main heading, the page promises one thing in search results and talks about another, and it ranks for neither.
How to fix it
Put the page's main topic, in the words your visitors use, into the title tag and the H1. If the most repeated words are not the topic, the text is about something else and needs rewriting.