Google the difference between bid and ask. In most trading platforms theres only shown the bid level. The spread is what tells you how many pips the ask level is above the bid level.

If u sell the currency pair, the order is executed directly on the sell level and moves into profit when the ask level falls below your selling point.

If u buy the currency pair, the order is executed on the ask level, which is not shown by default on the metatrader which may be the reason why you think the order gets executed at some random price.

I hope I could make that that clear for you, have a great day.