I dont think the FAT16 partition is 16GB as the maximum size for FAT16 is 2GB or possible 4GB.
https://en.wikipedia.org/wiki/Design_of_...ize_limits
My guess is that you have a fake USB flash drive. Can you reproduce the issue on a different make of flash drive (preferably a good make like SanDisk)?
Also, after copying on the ISO file, make sure to sync and eject the USB drive before rebooting or unplugging the USB drive.
Then check again that the ISO file is still on the USB drive under Linux again.
https://en.wikipedia.org/wiki/Design_of_...ize_limits
My guess is that you have a fake USB flash drive. Can you reproduce the issue on a different make of flash drive (preferably a good make like SanDisk)?
Also, after copying on the ISO file, make sure to sync and eject the USB drive before rebooting or unplugging the USB drive.
Then check again that the ISO file is still on the USB drive under Linux again.