I'm not sure it's right to mention another miner in this thread but I think it may help the author to fix the heavy hashrate bugs. The thing is that latest xmrig has managed to achieve very good speeds on heavy and it's stable. I've switched all my rigs to test it and it does the job. I'm getting  ~1800h from vega 56 and ~920-960h from 570 4gb and ~400 from r7 370 and ~580-600h from 560 4gb but unstable. So 560s are working with jce 0.33b4
It's open source so it's easy to see how it was achieved.