Why unusual page breaks, because there is a limit to how much can be fit on a page and when you keep adding to the page with text formatted as "keep lines together" and "keep with next" it has to break the page somewhere in violation of the rules you have set. That is why I recommended putting some text in Body Text or another style without these settings.

On any post other than your own, there is a green circle with a check mark in it that indicates the post has answered your question.

The recommendation that you spend an afternoon perusing John McGhie's work was if you wanted to know, really know, why you should follow the steps given by Shauna Kelly rather than just take my (and other's) advice to do it. Note that the problem solved by following those steps is even more evident in earlier versions of Word. You won't see it until you get into long documents and are editing, by then it will be too late.