Inconsistencies When Copying Files to SD Card

I have an Ultra 64GB microSDXC micro SD Class 10 TF card and am running Windows 7 Ultimate.

I have about 400 MP3 files to copy to the card.  All the files display the length (duration) values properly in Windows Explorer for the files on my hard drive.  After copying to the card, some of the files do not display the length (they show the name, date, and size correctly), but if I recopy them, they then do show the length (usually).

I have encountered this problem when copying the files to an MP3 player I have that has a 64GB internal drive.  But, when I copy the files to my flash drives (one a SanDisk, one a Lexar), I do not have this problem.  This leads me to believe there is nothing wrong with my files.

I’ve tried copying with a batch file (xcopy), Syncback, and within Windows Explorer, but I can’t find a solution to eliminate this problem.

Anyone have any ideas and/or suggestions?

Thanks for any help.