Available GPUs for mining:
GPU1: Radeon RX 580 Series (pcie 1), OpenCL 1.2, 8 GB VRAM, 36 CUs
GPU2: Radeon RX 580 Series (pcie 3), OpenCL 1.2, 8 GB VRAM, 36 CUs                                                           
GPU3: Radeon RX 580 Series (pcie 4), OpenCL 1.2, 8 GB VRAM, 36 CUs                                                           
GPU4: Radeon RX 580 Series (pcie 5), OpenCL 1.2, 8 GB VRAM, 36 CUs                                                           
GPU5: Radeon RX 580 Series (pcie 6), OpenCL 1.2, 8 GB VRAM, 36 CUs                                                           
GPU6: Radeon RX 580 Series (pcie 7), OpenCL 1.2, 8 GB VRAM, 36 CUs                                                           
GPU1: 43C 65%, GPU2: 47C 65%, GPU3: 47C 65%, GPU4: 45C 65%, GPU5: 47C 65%, GPU6: 50C 65%
Current -gt 71,71,71,71,71,71
Eth: Accepted shares 9095 (3 stales), rejected shares 282 (0 stales)
Eth: Incorrect shares 0 (0.00%), est. stales percentage 0.03% 
Eth: Maximum difficulty of found share: 11.4 TH (!!!)
Eth: Average speed (5 min): 0.000 MH/s                                                                                       
Eth: Effective speed: 53.04 MH/s; at pool: 51.45 MH/s                                                                        
                                                                                                                             
Eth speed: 0.000 MH/s, shares: 9095/282/0, time: 49:06                                                                       
GPUs: 1: 0.000 MH/s (1541) 2: 0.000 MH/s (1541) 3: 0.000 MH/s (1600) 4: 0.000 MH/s (1512) 5: 0.000 MH/s (1580) 6: 0.000 MH/s (1603)                                                           

I don't know why but at some point phoenix miner starts to show 0 hash rate, but it mines correctly on the pool, the share number increases with 0 hash.

I'm using ubuntu 18.04.
kernel: 4.20.6-042006-generic #201901310331 SMP Thu Jan 31 08:33:33 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
amd driver: amdgpu18.40-676022
Phoenix Miner 4.1c

At the fastest this issue happens after 15 hours of mining, but It popped up even after 4 days.

I also notice this in dmesg, but not every time, sometimes this error is there sometimes is not

kern  :info  : [Sun Apr 21 10:41:04 2019] traps: phoenix[9096] trap divide error ip:550ac1 sp:7ffdb110f230 error:0 in PhoenixMiner[400000+740000]
kern  :info  : [Mon Apr 22 09:23:49 2019] traps: phoenix[20905] trap divide error ip:550ac1 sp:7ffe62664970 error:0 in PhoenixMiner[400000+740000]