You have probably run into the reason that Cloud/shares are not recommended.
OK (with Calibre shut down)
Use the OS to copy the ENTIRE Library folder (the one with metadata.db) from where it is to a New folder on a Local drive.
The folder name will be the Library name once used.
Start Calibre (assumes it does not crash during start). If it does, you will need to use a command prompt window
Code:
calibre --with-library <full path to the library folder>
Once there that way, I am not sure how
to make this the new default using
Create/switch: use existing: <the new library folder>