Short positions (Sell orders) are opened at the Bid (Buyers) price and closed at the Ask (Sellers) price. Long positions (Buy orders) are opened at the Ask (Sellers) price and closed at the Bid (Buyers) price.
Please note that the chart in the trading terminal shows the Bid price. If necessary, the terminal may be customized to show the Ask price.
For your short position (Sell), the Stop Loss order was set at 1.2970. The price on the chart reached 1.2968, but that’s the Bid price. Given the spread of 2 points at that moment, the Ask price was 1.2970 (i.e. Ask = Bid + Spread = 1.2968 +0.0002 = 1.2970), your position was closed, because Stop Loss orders for short positions are executed at the Ask price.
In this case, the Stop Loss order was executed correctly, because the Ask price reached the level specified in the order.