The problem was EASY - too much overclock!
If you are used to artifacts and freezes due to ooverclock - so in in mining it is strange instabilty. First sign is MSI AB or any system proces start to use 60-80% of CPU even if miner is stoped! Reboot and lower OC by 5 pints backwards. watch your rig again until it is stable. then do another -5 and this is you stable OC.
Second sign of GPU error - fan speed in Claymore i 0% i logs.
Straight to the point! I had by myself such problems at the beginning, having overclocked my GTX 1060 3GB Samsung to +800 Mem Clk and spent hours parsing the logs, drawing charts, until I said - screw that 1.5 MH/s difference, my tranquility costs more than 5$/month that I'm chasing.
Working at +700 MHz like a charm (2249 MHz).