At a guess the OP has the stupid windows default for file/windows explorer, hide known file extensions.
I'm so used to NOT using that useless facility that I didn't spot the missing file extensions on the mp4 files (as Ezra has pointed out)
. That could explain a lot.
but it doesn't explain the fallback to DOS filenames.
We don't know whether these files have DOS filenames on just on the "file explorer" view or on the Humax itself.
If it is just on the file explorer, then there ought
to be some setting to correct this
. If these names are on the Humax, I suspect some program on the PC has corrupted the long filename before the files were moved to the Humax. (I know WinZip has a habit of screwing up archive names. I don't know if any other software does.)
For an accurate view of what's on the disk, use FTP.
A suggestion I should have made! I do this - but I don't have access to a Humax with CF.