Finally I find it! A know the problem why GPU's hangs on 12.1! Maybe not all GPU's but on my 280X and 270X it so...
I just read the logs.. and...
GPU's hangs if used option -ttli and temperature of GPU achieves this value.
After miner must to low intensity for cooldown GPU.
And 12.1 on this hangs GPU at all.
In logs appears string "Gpu # -ttli apply delta 1" and after that GPU hangs till restart.
To verify this I choose low -ttli for 270X and it hangs at chosen temperature!
Why my 280X hangs all time and 270X is not? Because 280X is hotter and more quickly achieves ttli temperature... And when I change intensity GPU allready was hot and therefore reach ttli temperature quickly...
I'm scared to run miner without -ttli... Will set tstop at the moment...
Claymore, can you check this and correct?
i'll try here...indeed i use -ttli too
I am allready installed back latest 17.2.1 and miner 12.1 runs without any issues or GPU hangs all this time. I was right, I just removed ttli option and add tstop until Claymore fix this.