So far I have tried 3 vega 56 cards. The first two I managed to exchange as they were having graphical glitches. The 3rd card (MSI Vega 56 Air Boost OC) hard crashes on games. The Taco (red led on card) goes to full it gets some coil whine it runs for 2 - 5 min then shuts the PC down (only during gaming). It's a new PC so all components apart from the PSU were sent back for testing with PCG and tested fine. The card even went back to MSI for further testing and came back as testing ok. I have purchased 3 new PSUs in an attempt to get it working 650,750 and 850 platinum rated PSUs. I have completely cleaned the drive and reloaded Windows, updated all drivers and BIOS and still having problems. I'm also using separate power cables for the GPU .
To make it interesting when I put the card in powersave mode in Wattman it will run BF5, Resident Evil 2 and Overwatch no problems. If I take it out of powersave mode and put it to default (balanced) I have issues. However, even in Powersave mode it will still hard crash on some games like Tom Clancey The Division 2 and Insurgency.
The card is stock not running any OC other than the one it comes with. The PC runs all games without issue with my old 290x installed.
MSI B450 Pro Carbon
Corsair HX 850