Given a 10 year walkforward test that is generally positive with a fairly smooth equity curve, but 1 recent year with a small loss, what are some suggestions from experienced walkforward testers to make all years positive? Some possibilities are changing the length of the IS and OOS periods, changing the trading system itself, changing the symbol(s) in the test or changing some other test setting. K-Ratio is being used as the optimization target and I've found it to provide the smoothest equity curve. Ideas appreciated. Thanks!