2. I have a few rigs on v11.5 and they are working for days until I restart miner to perform some new tests, but I always use non-overclocked cards and default bioses, I have to do it to exclude everything except miner in case of any problems. When you use miner on overclocked/unstable rig you cannot be sure that the reason of the problems is the miner, but of course you will blame it Try to reduce "-ethi" value, if it does not help you can use the version that works fine for you.