I did something bizarre and it actually worked. My Toshiba drives' permissions changed suddenly while using it. I am a strict mac user and I was trying to copy footage from an sd card. It really needed to be copied and I noticed that the driver had changed to Microsoft's NTFS. I had access to a window's system and computer (Boooooo) lol so I attached the Toshiba drive and SD card to that computer and copied the footage over. After it was done, I reattached my toshiba drive to edit on my mac and to my surprise my permissions had returned. In short i'd say to try connecting your drive to a Windows system then backt o your mac to see if it helps.