I think your problem is related to speed of USB. Please try same files at speedy USB disk. Same problem occurs if your network speed is slow. Like WiFi accessed scenarios.
So for play your files press play, and resume than retry after quickly. This will "cache" the beginning of the file and the file could play properly after...
TV could remember those things with internal cache, it's useful for generated thumbnails...etc. But when files are removed, TV detect it and deletes those thumbnails. At least, it needed to.
You can also try to play videos from NFS/CIFS mount vie SamyGO Extension like tools.
THanks
mpg codec problem over USB