This is the problem description: 1) open a file in excel, for example (myfile.xlsx) 2) when you open the file, (~$myfile.xlsx) temp file is created by default 3) the syncing creates also a file (~$myfile.xlsx.!sync) 4) in excel, save the file as (my2file.xlsx) 5) both (myfile.xlsx) and (my2file.xlsx) are synced, but the (~$myfile.xlsx.!sync) stays. If you modify a large number of microsoft office files, then you will forget that all this trash files are created.