Stop orders are executed based on market price. At times when the market price is volatile or based on the status of orders in the exchange, it may be difficult to find an opposite order to execute the transaction. At these times, your order may be executed at a different price from your Stop value.
In these cases, you can wait until the order execution completes or change your Stop value to match that of the exchange.
In addition, if there is not an another party agreeing to your order, there will be no order execution even if the market price reaches your Stop value.
If the "Average Position" row on the trade details screen is empty, this means your order has not been executed, and you will not be able to do a settlement.
At this time, you can delete the order itself, or change the order value to match that of the market price to ensure that your order is executed.