Yeah, I had an issue with massively slow hashrate on a brand new 390x.  Had the newest Crimson installed, bumped back to 15.something and my hashrate went to where it should be.  By bad hashrate I mean it was only putting out maybe 10 and it was never recognized by the pools.  So what I am saying is you need to do a search for a version of Crimson that will function properly for your setup.