I have same problem since firmware update is your HDD powered by the HUB USB or external power source? is file system NTFS?
My portable drive was powered by hub so not that but system is NTFS so wonder if that is problem
@Tallmat My portable hdd is 500gb so don't think it is disc size so back to NTFS
I've had exactly the same issue, I posted here:-
I lost connectivity to my drive in the USB port after a firmware update, BT sent me a new Smart Hub 2 which worked fine until it too updated its firmware, now the connection is lost again.