A bit more data from a DEBUG log.
Background: I mounted Google Drive to an empty Synology folder. I selected a random PNG file and chose to compress it to zip using Synology's File manager. That went well. The zip was created and uploaded to Google Drive and the File Station display updated to show the new zipfile.
Next, I selected that same PNG file, and dragged it to a folder for which I has read/write access. The copy transfer failed. Here is the relevant DEBUG log excerpt.
2021/03/07 17:44:29 INFO : 1000560.zip: vfs cache: upload succeeded try #1
2021/03/07 17:44:37 DEBUG : /: Lookup: name="1000560.png"
2021/03/07 17:44:37 DEBUG : /: >Lookup: node=1000560.png, err=<nil>
2021/03/07 17:44:37 DEBUG : 1000560.png: Attr:
2021/03/07 17:44:37 DEBUG : 1000560.png: >Attr: a=valid=1s ino=0 size=67804 mode=-rw-rw-rw-, err=<nil>
2021/03/07 17:44:37 DEBUG : /: Attr:
2021/03/07 17:44:37 DEBUG : /: >Attr: attr=valid=1s ino=0 size=0 mode=drwxrwxrwx, err=<nil>
2021/03/07 17:44:37 DEBUG : : Statfs:
2021/03/07 17:44:37 DEBUG : : >Statfs: stat={Blocks:4456448 Bfree:4126841 Bavail:4126841 Files:1000000000 Ffree:1000000000 Bsize:4096 Namelen:255 Frsize:4096}, err=<nil>
2021/03/07 17:44:37 DEBUG : : Statfs:
2021/03/07 17:44:37 DEBUG : : >Statfs: stat={Blocks:4456448 Bfree:4126841 Bavail:4126841 Files:1000000000 Ffree:1000000000 Bsize:4096 Namelen:255 Frsize:4096}, err=<nil>
2021/03/07 17:44:46 INFO : Signal received: interrupt
2021/03/07 17:44:46 DEBUG : vfs cache: cleaner exiting
2021/03/07 17:44:46 INFO : Exiting...
Any suggestions to solve the copy problem are welcome.