You can not run (with a Library) on a Networked drive with any reliability (if at all)
https://manual.calibre-ebook.com/faq...rked-drive-nas
If it did manage to run, it can Fail or worse, CORRUPT what you have.
Move it back to a UN SYNCED folder, the switch Caliber to the new location
Right click the Library Icon: Creat Switch: Use the Previously... :<select location>