On two computers (new devices, only Windows 10 Pro, Thunderbird, LibreOffice and Sync installed), I unstalled Sync. The uninstall process does delete all (!) of my Documents, Downloads, all personal data, even from other accounts. Furthermore, the windows computer cannot be startet again, I always get a BSOD loop. Maybe it has to do with the current update from Microsoft (Meltdown, Spectre)? The windows update was installed automatically before I uninstalled Sync.