Can you link an example page that has this problem?

Alas, the pages I am struggling are full renderings of proprietary online surveys, and I can't link to them. I tried a few other long web pages, and found that most work OK, but in a couple of cases, weird things happen that seem related to, but not identical with my original problem. For example,

https://www.facebook.com/WSUFF

Typical facebook page -- save to pdf as of just now gives seven mostly blank pages after the first, just repeating a small amount of material over and over. (For my survey renderings, the pages are pure blank, nothing repeated.)

https://www.nytimes.com/

New York Times home page, sometimes (not always) renders with a bunch of blank pages at the end, with the bottom of the page missing. Other problems in the rendering are visible, perhaps because the page is quite complex in layout. (In my case, nothing is omitted, and the layout is accurate other than the huge number of blank pages randomly placed.)

On the other hand, even quite long Wikipedia pages render nicely. I check every long page I come across, and will add other examples if I see any.

Those are login users sites only - so unless there is another user with access to those site they won't be able to fully see what is happening. And sometimes printing from web site introduces blank pages to the print as well so unless they give you a pdf file to download and print or open in acrobat reader to print this could be result of the site format pdf isn't compatible with pdf printing. Also you have to consider this could be a site protection on there site to prevent someone from just downloading the site news? You should also contact their site support and how to print a pdf or article from their site and if there is a different printing format setup you need to setup to print the articles or pdf from their site.