Resolve this yet?

all pcie slots set to "Gen1"?  (including the 16x)?

I to run an Asrock board with Sapphire 8GB SE Micron and have odd issues.  (even stock)
With the asrock h110 pro btc+ and Windows 10 (1703 or 1709), I can only mine if I have the Integrated GPU on.  When I set to disabled, my RX580's lose "OpenCL" which is required to mine.
Currently have 8 of these identical GPU in the rig on Silent mode, and can only mine for approx 6 hours before the AMD driver crashes.

This might help your situation?  See latest Beta Bios revision as of Feb 27
http://www.asrock.com/mb/Intel/H81%20Pro%20BTC%20R2.0/#BIOS