This could be a Fat 32 issue, open Disk Utility and look and see if any of the drives are Fat32 if they are first try copying smaller amounts of data (no larger than 4GB at a time) over to the drive.
Most of my extenal drives are converted to Mac OS Extended (Journaled) or NTFS (required mac software
NTFS for MAC $20 Tuxera NTFS for Mac $31 or
NTFS-3G free with
Macfuse free both must be installed. I prefer NTFS for MAC install and forget.
Let me know how you go.