Write Closed but Windows 10 won't provide safe to remove flash drive

This is both a Writer question and a Windows 10 issue.

I close Libre Writer and all the other programs I had opened but when I
click the flash drive icon in the "system tray" (lower right) to receive
the Safely remove the flash drive it keeps displaying that I need to close
programs.

I've check each program along the toolbar (on the bottom) and none are open
but it still won't give the OK to pull the flash drive out.

I've Googled this and reads both that you can just pull the flash drive out
as its plug and play and others say the flash drive will stop working oif
you keep pulling it out with the "Safe to Remove" message.

Your thoughts and suggestions are greatly appreciated.

1. Separately open a window of the folder showing the document you are
    opening. Make a backup copy from Windows. Once your document is
    open, a temporary file should be created in that folder. When
    closing the document, the temporary document should disappear. If
    the temporary document does not go away, delete it.
2. Run Windows 10 Task Manager and look for any surviving LibreOffice
    programs running. If yes, kill the program, then see if it is safe
    to remove drive.

If either of these work for you, see "How to Report Bugs in LibreOffice at https://wiki.documentfoundation.org/QA/BugReport

These are the two things I found that caused LibreOffice to not let go of a file.

Hope it helps.

When Windows displays that programs need to be closed, does it display any
of the program name(s)?

If yes, what is the name or what are some names? (If Paul's response fixed
it, never mind.)

Using openfiles.exe (from Microsoft) you can see which files are open.

(link: https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/openfiles )
<https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/openfiles>

first you have to enable it using: openfiles /Local ON    (and do a reboot)

After that you can query with files are open using : openfiles /Query .....

More details on how to use this are given on the link given above.

Thanks! Very handy to know about.