Severe slippage

At 13:00,27th,June,2019,my position was closed at 1406.14 while I set the stop-loss price at 1405.65.The highest price in that minute was 1405.75,with 0.2-1.5 spread existing in the platform.Since the market was out of volatility and gap,but the position-closed price was 4.9 higher than stop-loss price.