Hmm. I am not that familiar with Filestream. Are you? As far as I know, it’s an “on demand” way of syncing files in the cloud (Google Drive servers) with local hard drives. Is that correct? My first thought would be, since Google Drive’s non-Filestream “Back up and Sync” method of keeping local folders synced with other team members is *somewhat fragile* for an InDesign/InCopy workflow, that imposing a new way to sync files w/Filestream is just asking for trouble.
BUT you’re saying InCopy can open *some* InDesign files and the links to InCopy stories are intact. Is that correct? But for “15 or 20” when you open the INDD in InCopy, it says it has no linked InCopy stories?
Helen, can you open one of the bad boy InDesign files in InCopy, and go to Window > Links, to see if any links to ICML or images appear? If so, can you hover over one of the links to an ICML file to see the file path? See if that file path matches what your designer sees when she opens the INDD in InDesign on their end.
If you *don’t* see any ICML files listed in InCopy’s Links panel, but your designer does (for the exact same INDD file … make sure they’re opening it from the same folder), then have them make a change in the InDesign file, something major/easy to spot, but temporary), and save it. Give it a minute, and on your end, open it (or re-open it) to see if you can see the change to the InDesign file.
This will help troubleshooting.
AM