ok, it seems that my inability to mine ETH or ETHOS using RX 580 is due to driver. I updated to AMD's latest 18.10.2 and it started erratic mining on ETH. I revert back to 18.10.1 and for 2 days I didn't experience 0 Mh/s. I'm gonna try xmr-stak-v8 and see if I get "invalid" or not.