Bookmarks no longer functional on my iPad

For the last few years, I've been able to access the bookmarks in very large manuals after transferring to my iPad.  ie: I go to the Bookmarks prompt (Table of Contents), scroll down thru several chapters /index to get to the specific subject I need, click on it, and I could jump to the specific page.

As of a few months ago, some of the bookmarks in several manuals are no longer functioning.  ie: I click on a bookmark and nothing happens.

All bookmarks are working perfect on my Win10 PC, but no longer on the iPad.

ios Acrobat - 18.02.28 (182229)