Have you try to increase voltage to theses 2 cards? In the log the DAG seems to be not created. Only to discard...
Slightly lowered the core frequency, slightly raised the memory voltage on all GPU and the oddities stopped.
Uptime: 3h 22m 35s
GPU 0 GPU 1 GPU 2 GPU 3 GPU 4 GPU 5 GPU 6 Total
Speed (mh/s): 24.56 24.57 23.89 23.46 22.41 24.57 24.58 168.03
Pool (mh/s): 21.20 22.97 22.97 27.21 25.44 22.61 21.55 163.95
Best Share: 295.4G 182.8G 133.3G 168.9G 222.4G 677.4G 7.3T 7.3T
Shares (A/S/Hw): 60/0/0 65/0/0 65/0/0 77/0/0 72/0/0 64/0/0 61/0/0 464/0/0
Power (W): n.a. n.a. n.a. n.a. n.a. n.a. n.a.
Efficiency (mh/s/W): n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a.
Temps (deg C): 62 67 58 66 61 59 63
Fan Speed (%): 93 98 73 90 74 90 93
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Thanks for the help!