When you share a Flipbook or Folder link on LinkedIn for the first time, LinkedIn will first display the Folder's SEO > Description text (See this article describing how you set that text).
LinkedIn will then cache that Folder level SEO Description text for at least one week. This means that even if you change that text on the Folder and share an entirely different Flipbook link or the Folder link again, the previous text is going to show until LinkedIn clears that cache.
Unfortunately, LinkedIn does not provide a way to clear out that cache on their side so if you would like to share a link, and make sure that the old text does not show, you can add a simple query append to your link such as "?1"
For example: goingdigital.uberflip.com/t/10418?1
By adding a query append, LinkedIn will not recognize the link as being shared before, and hopefully will display the new Folder description text, or at the very least will NOT display the incorrect text (no text instead)