--scrypt -I 17 -g 1 -w 256 --thread-concurrency 12000 --gpu-engine 1125 --gpu-memclock 1500
same card, run with this setting - 3 days 24/7 - no freeze 452 - 454 kh/s
Have a 5 card gigabyte 270 rig and I keep having either of the following things happen. Display driver crashing constantly over and over like this

or I sgminer.exe will crash.
I tried your settings and it ran longer without a crash but I was getting hw errors. For the 3 hours it ran gpu 0 had 1 and gpu 3 had 10. Starting to wonder if gpu3 is shot....
try --scrypt -I 19 -g 1 -w 256 --thread-concurrency 11776 --gpu-engine 1050 --gpu-memclock 1500EDIT: try --scrypt -I 19 --thread-concurrency 2400 --gpu-engine 1129 --gpu-memclock 1475 seems to be the best my cards can do stable, 479~ khs
Been tinkering for days trying to find a good stable setting and this seems to be it as for now. Good luck.