I had the same problem and it was caused by the asrock h110+. Such a piece of junk if you want to use it with vegas...
I'm using an ASRock H110 with 5x Vega (soon to be 8, once I get my 240V circuit set up) with no issues. I have seen mixed reviews, so it's very possible that with such niche hardware, the failure rate is a bit higher.
I use both mining expert and 110 mobo with each 7x vega 56 on them. They both behave the same, a few freezups a week for each board. Stable enough for me using a auto soft reboot script, but not 100% stable.