Some of my .mkv files are not showing on MAC

Hi everyone,

I have some .mkv video files on my old Windows 7 laptop.

I tried to transfer them to my iMac running on High Sierra 10.13.3 copying them on an external drive. However, when I open the drive on my iMac, some of the files are missing.

I have tried to transfer the files via an SD card and it does the same...some of the files do not show up on my Mac. I also tried to do the same on my Mac Book Air but the same files are still not there...when I plug the external drive back to Windows, the .mkv files appear.

I have tried a few things, including showing the hidden files on Mac with the command in Terminal without success.

It is very bizarre as out of 40 .mkv files, there are just 5-6 that disappear on Mac. The files seem to be fine as on windows, they open fine and the video plays nicely.

I would very much like to transfer them to my Mac as my Windows laptop is very old and about to die and I do not want to lose them.

Many thanks,

Simon