I've looked through the forum but cant find a solution

I have Acer X3995 running windows 8.1
I have a 4 port USB 3 hub connected (with 4 x USB drives attached) and 1 portable USB 3 drive.

When copying large amounts of data to the drives they will disconnect from the system and then reconnect.

The system will also hang on reboot if the drives are connected (solution is to disconnect, reboot and reconnect when windows logo is present).

Is this simply a USB 3 instability issue I have to live with or is there a something wrong with my drivers?

Please help.