What config did you use with xmr-stak-amd? Vega56 doesn't like high intensities with xmr-stak. cast-xmr is way better for vega56 if you are not concerned with closed-source risk ))
I'm running 2016/1600 and 2016/1736. Both have the same issue.
I've been following the reddit definitive guide and it mentions no problems with those intensities.
At some point I remember lowering them to 1920 / 1524 but was not stable either.
Can you suggest some intensities to try ?
PS: yes, I don't like running closed source. I even compiled stak-amd myself, but it makes no difference vs. the stability issue above.