I've been using MT4 build216 to do some backtesting with model "open prices only". My EA uses stop orders to place trades. Usually I check a number of trades manually to confirm that the EA performed as intended.
during one of my checkups I noticed that a few stop orders should have been triggered but wasn't. that is, price had gone past them but somehow they were not activated.
to confirm that MT4 had indeed overlooked these orders during backtesting I ran the EA again with model "every tick". this time the stop orders were triggered correctly.
this could indeed alter the outcome of EAs' backtesting results, if the overlooked trades happened to be very profitable ones. it's not always possible to get enough 1 min data to use the "every tick" model, especially with long-term trading systems.
during one of my checkups I noticed that a few stop orders should have been triggered but wasn't. that is, price had gone past them but somehow they were not activated.
to confirm that MT4 had indeed overlooked these orders during backtesting I ran the EA again with model "every tick". this time the stop orders were triggered correctly.
this could indeed alter the outcome of EAs' backtesting results, if the overlooked trades happened to be very profitable ones. it's not always possible to get enough 1 min data to use the "every tick" model, especially with long-term trading systems.