This is a general problem one will face when they use external USB storage. Most of the USB mass storage vendors, packs their disks with FAT32 formatting (not sure why). This limits us from copying a file which is more than 4GB. It’s a limitation with FAT32 partition. Another thing I noticed is, we cannot copy more than 100GB into a FAT32 formatted USB drive though the drive capacity is more than 100GB.
So, if your USB storage disk of any size more than 100GB, I prefer formatting it with NTFS before you really use it. If you already have some data in it, and cannot really copy it to somewhere for formatting, you can give a try with “covert” command which coverts your USB drive to NTFS from FAT32 without losing data. Try at your own risk, I cannot guarantee. Chose this utility if you really don’t care or don’t have a place to back up your data