It "loses" files? How is that even possible? How is it formatted?
ETA: I'm sure this is too obvious, but...they're not hidden, are they?
Sorry, this is a long response:
I use the external drive to have videos - both movies and non-movies - for me to watch on my laptop.
It also kind of acts as an emergency final level backup of files.
The storage drive is 4 TB hard drive.
My laptop itself has a 500 GB SSD and a 2 TB Hd which replaces the DVD rom
I have too many video files to be able to store just on the 2 TB Hd but I keep movies on it and a few other items.
I use a program called "Karen's Replicator" to duplicate files over the the external. It also deletes files you have deleted. There are of course setting to do this. It is an older program but simple to use and allows me to transfer only files that have been changed and/or new files.
Use it to transfer files to the other computer across the network and to my desktop external for backup. I also used it to transfer to the 2TB WB portable drive. None of these have ever had an issue with the program. Windows file explorer is not "smart" where it will do something similar. Deleting the directory in windows and then copying all of the files takes hours.
When I got the drive, I transferred movies and other videos over to the new portable. I noted that some of the videos were corrupted (ie: they would not play) soon after. They were on the drive however. Kind of frustrated me still.
I ran "Sea tools," the Seagate utility and it claimed to have fixed all errors or that there were no errors. Just in case, I deleted all videos and movies. I used windows explorer to save them then. As far as I have been able to tell, all of the files are there and they will play.
Just Saturday, I got a DVD I ordered from Half.com (part of eBay) and made a copy of it. I do a two step process where I fist make an MKV of the file and then make an MP4 of that. MKV files are very large.
I plug in the portable and used Karen's replicator to copy changes from my movies folder (and there are sub-folders in it) to the portable. It appeared to have duplicated changes. I plug the portable into my laptop and use Karen's replicator on that end to copy to the internal 2 Tb. Doesn't copy anything. Check the drive and the file is gone.
I did check and I have the computer set to show hidden files. I actually hate hidden files. trying to think if there is some new security feature on the drive or with Windows 10 messing me up. I am running an anti-virus on both my desktop and laptop.
It does piss me off that it did this but I keep enough multiple backups that I am probably OK. My issue is as much that I use the portable to backup documents from my laptop. If something happens to my SSD and a file is corrupted or lost, that could be really bad.