• Charts on the MetaTrader are created using the Bid Price. 
  • Closing of Buy Orders are triggered by the Bid Price so you will see the chart line hitting the Stop Loss. 
  • On the other hand, the closing of Sell Order are triggered by the Ask Price, which is not visible by default, hence why the Stop Losses of Sell Orders may happen on prices not visibly seen on the Chart. 
  • The Ask Line can be enabled by right-clicking on the chart, selecting properties, and enabling the option.