File Share Encryption

I am usinSymantec Drive Encryption 10.3.2.MP13 on Windows 10 Pro 64 bit PC.

 I have several PGPdisk encrypted file containers and I can decrypt them if they are on a physical SATA drive on my computer or a USB thumb drive.  They mount as a drive letter in Windows and then I can open/edit the files, etc.

However if these PGP disk container file are copied to an external USB hard drive (3TB, 4TB, etc) , then if I open the file, I enter my PGP password as usual and it mounts the drive in Windows, BUT it will then say that new virtual drive is not readable and needs to be formatted.

If I take the same PGP disk container file and copy it to an internal hard drive (or 128GB USB thumb drive) and open it, then it works fine.

What could be the problem here and how I can I possibly fix it or work around it?  Thank you.

And to add more information about this issue, sometimes when I copy the files over the encrypted PGPdisk container to another drive, such as internal SATA, I can then enter my password and it creates virtual drive where I can get to my files, but they are then all read-only.  I have to copy them again to another drive for them to be read/write again.

It might have something to do with the drive translation over USB 3.0.  PGP Virtual Disk service was designed with USB 2.0, and still has some quirks on occaision with USB 3.0.

This type of behavior sometimes occurs on a flash drive as well, but usually external drives connected via USB 3.0 are more susceptible to this issue.  If possible, try a USB 2.0 port if you have one on that system.