Forum Discussion
Restrict shareing files in a document library to members of that document library
An additional three questions from me in order to understand your situation better.
1. Are there any sensitivity labels in play that might help? --> Really helps in depth with your issue
2. What are the currents sharing setttings for Files and Folders?
3. Could you clarify the "can now see the Managers Document Library listed in SharePoint" part? As in: the user can see the URL of the library?
Regarding to number 2, I've added some pictures of some setting options that might help.
Files and Folder links --> You can specify for SharePoint and OneDrive who can access
In addition, if it's set on "Anyone with the link" you can set an expiration date (for instance: access by link expires after 7 days". I myself find that setting an experiation data helps users keep track of what they've shared and what not 😀 (mostly I used 30 days)
Hope this will help or maybe at least dive a bit more into your question