Hi,
This is to report that both WD and Seagate are now playing the files right, so the issue was coming from HDD errors which were resolved using chkdsk/f tool from Windows.
I would not recommend using SeaTools as it did not help at all and generic long test would last forever and the other tests would not do anything.
I will now have to investigate what is generating the errors on the disk when copying files, but this is not in the scope of that forum.
Great thanks to all who have helped me resolve the issues and I will be able to watch a great movie with family tonight thanks of you!
BR