I think this is more random problem. I upgraded drivers from 16.7.3 to 16.8 and it worked well over night. I guess it will keep on working well. I was thinking about using -r option to set 30 min time to force reboot and then keep bat file in the startup with delay of 30 sec. But that means I will lose 3-5%  mininig time further.

But anyway, so far so good.. it is working for now
thanx for your advice