Copying 100,000 files from USB to USB, some files are missing

So I just copied 104,639 files from a USB HD to another USB HD. I checked unattended operation "replace".

Afterwards, many files were missing from the destination. It is as if the copying just kind of stopped somewhere and also skipped some files.

Now, I am copying the files again, using "skip identical" and it seems to be copying a bunch of extra files. I hope afterwards, source and destination will be identical.

I am not sure how this can be reproduced, but I used a USB 3 NTFS HD as source and a USB3 EXFAT HD as destination. Both are connected via USB 3 hub.

Is there an error log somewhere that shows me why some files were skipped?

It finished and the last 600 or so files where all not copied with the first run and now copied over on the second run.

I am now running the copy procedure a third time (without checking unattended) and there are still some files being copied. So even after two runs, not all files are copied.

I think this is very disturbing. Is there an additional check I can enable so Opus will actually test that files made it over? It feels as if Opus is completely ignoring whatever error it encounters or the OS throws when it fails to copy a file.

I would prefer it if Opus checked the destination file is there and maybe retry at least once if it isn't...

The Unattended window should say if any files were skipped and why.

Is there any pattern to what was skipped?

If the same copy (same files, source and destination device) is done using another program, do you get similar results?

Checked antivirus logs to see if anything was automatically cleaned?