Frankly I am surprised enterprise worked flawlessly using an external drive.  QB is notorious for not playing well with external drives.  Personally I think it has something to do with the wake up command QB has to first issue to access the drive, but who knows.

I back up to a computer local hard drive, and I have a script that runs to copy from the local drive to the external drive and to a google drive folder so it syncs to my account in the cloud

Sorry I couldn't be more help.