Table of contents - page numbers being pushed to next line even with plenty of space

Hello, I'm setting up a book in Indesign, it's a 2nd edition. Have put in the Table of Contents, but for a few of the entries the page numbers are randomly getting pushed to the next line. (See screenshots).  It only affects a few of the entries, most are fine. I've fiddled with with the Tabs in Paragraph style to try to fix it (it is right aligned as I saw suggested in another post). As you'll see from the screenshot there aren't any extra tab spaces or space, just the tab. (I manually checked too). I checked that the Paragraph style is properly applied and that there aren't any Character styles applied. Anyone have the same issue and able to solve it? Many thanks!