Just wanted to chime in here that I experienced something similar to this earlier this year and made a post about it. Whenever I added files, random files/folders would disappear from the drive. I can also confirm that it wasn't just files in the upload queue disappearing and definitely not some automated software deleting my files since I didn't have anything like that running. I still don't know exactly what caused this but I've since deleted the entire drive and made a new one since I figured something was wrong with the drive and didn't want to keep looking for random missing files. So far I haven't come across the problem again.