Inconsistent links when outputting to PDF

[scheffbd]

When I output a FrameMaker book to PDF, links from the generated Table of Contents to pages in the manual are inconsistent. On some TOC items, the entire line (paragraph number, paragraph title, and page number) is a 'clickable' link, but on some random lines -- such as paragraph 4.40 in the example screen capture below -- only the paragraph number is a clickable link. Paragraph 4.40 is formated no differently than 4.39, 4.41, 4.42, etc.; so I can't see any reason why the rest of the line isn't part of the link.

Is this a FrameMaker bug, an Acrobat bug, or is there some way to fix this other than manually extending the link across the entire line each time in Acrobat? 

I'm using unstructured FrameMaker 2019 and Acrobat Distiller DC.

[Jeff_Coatsworth]

How does it behave when you look at the TOC in FM? What parts are considered xrefs?

[LinSims]

Are the odd ones tagged with same paragraph tag as the others that work in the text, even though the end result looks the same?

If so, I'd check the reference page to be sure that the corresponding TOC tag doesn't have a character tag in the middle of it. That's the usual reason for this sort of thing to happen.