This would depend on the model / brand of gate opener that you have. Some determine the stop position through a learning sequence. For those openers when doing trouble shooting the first thing we would have you do is go through the gate opener's stop position learning sequence and see if it makes it through without error. Other gate openers have a physical limit switch. Many that have physical limit switches have a way to tell if the limit switch is being triggered through a light on the board or using a multimeter to check for continuity.