Yep, this was the solution for me also. I kept getting “Error creating object. Could not create backup copy.” when trying to save changes to LibreOffice “*.ods” documents on my company’s Unix server, while working at my Manjaro Linux workstation. No fixes I tried worked until I found your “add nobrl to the /etc/fstab cifs mount” suggestion; that worked! According to one web page I just looked at, “nobrl” means “prevents sending byte range lock requests to the server”. That’s gibberish to me (might as well say “prevents hypervalination of the verticulated encabulator” for all the meaning it conveys to me), but hey, it works, so I suppose I shouldn’t knock it.
Windows 10, LO24.8.3.2 Experienced a corrupted file in Writer, and after that could not save existing files in Writer or Calc, although I could open new files and save them. I got this error message:
Error saving the document (File Name)
Error creating object.
Could not create backup copy
Did a factory reset in Safe Mode and it worked.