Same issue with 18.4.1. Goes from 27k+ to 0. Crash, restart, repeat. This is with Compute mode on or off.
The old blockchain drivers still work well. Have not yet tried with 18.3.4
09:20:17:882 3634 ETH: GPU0 27.570 Mh/s
09:20:20:720 3634 ETH: checking pool connection...
09:20:20:721 3634 sent: {"worker": "", "jsonrpc": "2.0", "params": [], "id": 3, "method": "eth_getWork"}
09:20:20:773 3634 buf: {"id":3,"jsonrpc":"2.0","result":SNIP]}
09:20:24:900 360c GPU0 t=62C fan=35%
09:20:25:696 3608 em hbt: 0, fm hbt: 15,
09:20:25:696 3608 watchdog - thread 0 (gpu0), hb time 2953
09:20:25:697 3608 watchdog - thread 1 (gpu0), hb time 2609
09:20:28:200 3634 buf: {"id":0,"jsonrpc":"2.0","result":}
09:20:28:200 3634 ETH: 05/08/18-09:20:28 - New job from us1.ethermine.org:5555
09:20:28:201 3634 target: 0x0000000112e0be82 (diff: 4000MH), epoch 185(2.45GB)
09:20:28:201 3634 ETH - Total Speed: 0.000 Mh/s, Total Shares: 1, Rejected: 0, Time: 00:02
09:20:28:202 3634 ETH: GPU0 0.000 Mh/s
09:20:30:595 3634 sent: {"id":6,"jsonrpc":"2.0","method":"eth_submitHashrate",SNIP]}
09:20:30:632 3634 buf: {"id":6,"jsonrpc":"2.0","result":true}
09:20:30:735 3634 ETH: checking pool connection...