The trigger evaluates the condition and if it's true it activates, false forces it to deactivate.
The code I posted is an example of that in operation in a repeating trigger.
First it has to activate so it can then deactivate.
If you 're getting some results then I suspect it's from something else.
If all you want is a player to enter the trigger and it to activate you need something like this
Hides the object
trigger1 setTriggerstatements ["true", "X1 hideobject true",""];
Reveals the object when player enters the trigger.
trigger2 setTriggerActivation ["WEST", "PRESENT", true];
trigger2 setTriggerstatements ["this", "X1 hideobject false","X1 hideobject true"];
Adjust the "WEST" to match the side of the unit your trying to detect.