New problem after the new release 6.1.4 has solved the problem about "The directory name is invalid".
Now I have new problem on all the clients with MS Windows 10 1709 (Fall Creators Update): when I open an .xlsx or .docx with MS Excel 2016 and MS Word 2016 (latest patch release 8625.2121) and I save the files, the two programs crash immediately with the message "Microsoft Word/Excel has stopped working". The files are not saved and .tmp files appear in the shared folder (one .tmp for every saving attempt).
This! Applied updated last week, however, getting this error this morning (albeit with SketchUp files, not word files). Seems to apply only to me, as all our other workstations don't have Fall Creators update yet. Just cleared SMB cache again, so we'll see if thats a temporary fix for now.