Hello, first sorry for my poor english,
I've the same issue with the same graphic card and a lot of people has it too ( people withe the gigabyte one too )
I tried everything i could, UC/OC, all drivers, different psu 700w 80+, all settings and i still keep crashing randomly.
Temp (hotspot) are ok, everything seems fine. And the card keep crashing.
There is so much people having this issue that i guess its drivers related, or at least i hope.
Is yours hard crashing i.e does the power go off? Also how can the store and MSI test the card and it is fine?
Yup the graphic card power goes off, no more red light + black screen + fan at max speed.
I am having this exact same issue. System crashes at random (gaming or general use) shortly after Gigabyte Vega 56 installation. (MSI Z77A-G43, i5 3570k, 750w PSU) Drivers are up to date and everything. All monitors go black, system is unresponsive, and GPU fans hit max speed.