When you mine in stock, does it also crash?
It also crashes when I mine stock... Have no problems mining zcash with higher clocks... What could be the problem? Looks to me like its software problem.
I had the same problem with the same error while mining skein algo with 3 evga ftw3 1080ti than I changed the mobo because of something else and everything is working fine now. My problem was the mobo itself maybe your motherboard also having issues with this algo and miner. If you have another mobo you can give it a try.
I want to buy another 1080 ti, I'm between Gaming X (which I already have) and FTW3. what is the hashrate you get on your FTW3 for example mining ZEC with 70% of pw.