I noticed that speed start to flactuate after recieving new job... Maybe it's nicehash problem...
Why didn't you say so? i've a special sync for nicehash, with dedicated netcode (Nicehash is a lot more netcode-aggressive than other pools).
Please try on a normal pool, if it gets stable, so here's the problem.
Maybe SRB doesn't have that nicehash special, so in this precise case, it avoids the problem.
I'm preparing v8, which will be like -sync, but :done, online is the
0.33b8 GPUCrash on old HD cards fixed (was a typo in my old card's code)
Light optim for modern cards on Heavy/forks
edit: ok I found my bug on Nicehash netcode, but too late to fix in b8, that will be for b9
meanwhile please test on a normal pool

B8 is working but is terrible slow on CNv8 and HD6990. And it looks like there is no warm-up. All hashrates are more less the same.
On b4:
23:17:16 | Hashrate CPU Thread 0: 62.82 h/s
23:17:16 | Hashrate CPU Thread 1: 61.83 h/s
23:17:16 | Hashrate CPU Thread 2: 61.17 h/s
23:17:16 | Hashrate CPU Thread 3: 61.29 h/s
23:17:16 | Hashrate CPU Thread 4: 62.33 h/s
23:17:16 | Hashrate CPU Thread 5: 63.39 h/s - Total CPUs: 372.81 h/s
23:17:16 | Hashrate GPU Thread 6: 281.88 h/s - Total GPU 1: 281.88 h/s
23:17:16 | Hashrate GPU Thread 7: 283.53 h/s - Total GPU 2: 283.53 h/s
23:17:16 | Hashrate GPU Thread 8: 283.44 h/s - Total GPU 3: 283.44 h/s
23:17:16 | Hashrate GPU Thread 9: 283.90 h/s - Total GPU 4: 283.90 h/s
23:17:16 | Hashrate GPU Thread 10: 282.16 h/s - Total GPU 5: 282.16 h/s
23:17:16 | Hashrate GPU Thread 11: 284.00 h/s - Total GPU 6: 284.00 h/s
23:17:16 | Total: 2071.70 h/s - Max: 2071.70 h/s
On b8:
23:11:05 | Hashrate CPU Thread 0: 61.65 h/s
23:11:05 | Hashrate CPU Thread 1: 59.82 h/s
23:11:05 | Hashrate CPU Thread 2: 59.10 h/s
23:11:05 | Hashrate CPU Thread 3: 59.43 h/s
23:11:05 | Hashrate CPU Thread 4: 61.05 h/s
23:11:05 | Hashrate CPU Thread 5: 61.77 h/s - Total CPUs: 362.79 h/s
23:11:05 | Hashrate GPU Thread 6: 246.07 h/s - Total GPU 1: 246.07 h/s
23:11:05 | Hashrate GPU Thread 7: 246.56 h/s - Total GPU 2: 246.56 h/s
23:11:05 | Hashrate GPU Thread 8: 246.83 h/s - Total GPU 3: 246.83 h/s
23:11:05 | Hashrate GPU Thread 9: 247.18 h/s - Total GPU 4: 247.18 h/s
23:11:05 | Hashrate GPU Thread 10: 246.49 h/s - Total GPU 5: 246.49 h/s
23:11:05 | Hashrate GPU Thread 11: 242.80 h/s - Total GPU 6: 242.80 h/s
23:11:05 | Total: 1838.70 h/s - Max: 1853.28 h/s
And after 3min of hashing two GPU threads has stack. This time different GPU then ordinary one.
Maybe I should change the config file somehow?