I think I understand what you're describing: something that acts like a page break but there's no page break command there to remove. I would check the formatting on the paragraphs above and below. It may just be that "keep together / keep with next" is checked for no reason. This has happened for me and I can't explain why it happens but the fix is easy.
Thanks Dorothy. That makes sense. In the combined volume, page 218 of the later TOC won't be included (because it applies to later volumes) - do I need a TN or is doing a combined page number on the next body page enough?
Yes. The shortform can be part of a larger word when it's at the beginning of a word and followed by a consonant (except y), so "llc" would be read as "littlec" (doesn't matter that the latter is not a word).