SharePoint Document Library not unsyncing. Ideas around issue?

From my (ever growing) list of things to do if OD4B doesn't behave properly, like not stopping to sync:

• Turn on the options in Explorer so that you can see every file, including system files and hidden files.
• Check if you can see "sync icons" or "red marks" on some documents. (Note that you'll have to look at every directory within that document library. Sometimes the "sync icon" doesn't get propagated to the top of the directory tree.)
• Some of Windows' files cannot and will never be synced, like "desktop.ini" or temporary files from Office.
• If you see "desktop.ini" check the SharePoint document library with a web browser. If you see the file on SharePoint delete it.
• Otherwise just delete "desktop.ini" in your Explorer.
• If you see temp files from Office, open the corresponding Office document with Word, Excel, whatever. Make the document active and close it (without saving). The temp file should go away.
• If you don't see a corresponding Office document just delete the temp file.
• If you see "sync marks" on Office documents,
  • open them and close them (from the Explorer)
  • open them, save them again (from the Explorer)
  • open them directly via the Office application and not via the Explorer
• If that doesn't help, move the files out of the shared library (like on the Desktop), wait a little, and move them back.
• If you see marks on a folder, move the folder out of the library, wait, and move it back.

Most of the sync problems can be solved by simply opening the "erroneous" files.

The worst thing that you may encounter is that you don't see any sync icon at all. If that happens you can only try to un-sync that library, delete in on your computer, and sync it again.

If you cannot un-sync a library you are almost always better off with stopping everything and clearing the cache according to

https://support.microsoft.com/en-us/kb/3038627