I'm using Windows 10. When I run Sync Toy 2.1 (64) I consistently get errors when attempting to sync/echo Excel.xlsx files from my C: drive to my NAS drive.
Excel.xls files work OK; and, Excel.xlsx files copies ok to D: drive and to flash drive.
Also, new Excel.xlsx file copy OK. Problem only exists with overwriting existing Excel.xlsx files from C: to NAS drive (\\192.168.2.1)