The issue here sounds like the drive is formatted as FAT 32 and this is a problem connected to an OSMC device and using explorer to transfer files from Windows. In this case smaller files will transfer but there is no progress dialog. Files over a particular size (fuzzy memory is leaning toward a couple gigs) will not successfully transfer. In addition I seem to recall that if you tell a file to delete on said drive from windows it will be removed from view but the space is not freed. Also when you have one of these failed transfers, the space that was taken up by what was transferred will not be freed. In short, if your going to touch the drive over SAMBA don’t use exFAT. NTFS did not seem to have any of these issues. I would assume any Linux file system would also not have an issue but I personally didn’t test that.