I've never seen any hangs with Fiji (Fury) and it's my main development card.

There is a VBIOS switch on the side of the card. When the computer is powered
off, flip the switch to the other position. See:
http://www.legitreviews.com/wp-content/uploads/2015/07/sapphire-fury-switch.jpg

The picture shows the "best performance" position. (also higher power
consumption) Hawaii (290, 390) has the switch too.

I have the switch in the same position as on the picture. It's known to be the
only stable position for my 290, and it's the only position I tested with my
Fiji.

Remember to flip it when the computer is powered off.