I've found that in my scenario using "array get closest game object" finds the wrong (the furthest) result between the 2 objects I have on the array, though if I replace it with an array maker array list and swap the action for "array list get closest game object" in the the same scenario it finds the correct (the closest) game object.
Using Unity 2017.3.0f3 and the latest stable release of Playmaker.
More details can be provided if this cannot be replicated.