Q: iCloud drive no longer syncing files Windows 10

I have Windows 10 Build 10565 and iCloud 5. Everything was working fine syncing all files, photos calendar, contacts etc, until Windows 10 updated to a new build (sorry don't know the number) and iCloud updated to version 5. I rolled back windows to 10565 but iCloud is has stopped syncing files. It downloads between 300mb and 700mb of files and then stops - there are about 7 GIGABYTES of files. Why has it stopped downloading files - is there a way to discover if one file is causing a problem or if the application is the problem. I'm about to uninstall iCloud version 5 and try 4.1.