This issue often confuses beginner traders, especially when dealing with Sell positions, because the spread isn’t always taken into account. Sell trades open at the Bid price, and most charts display the Bid price as well. However, Stop Losses for Sell orders are triggered at the higher Ask price. As a result, a Stop Loss can be hit even if the chart price hasn’t visibly reached the Stop Loss level on the chart.
You can display the Ask line by right-clicking on the chart => Properties => Common (“Show” for MT5) => Show Ask line (Show ask price line for MT5).