So the code you have there is not ‘spawning’ a mesh as you described in the original question, it is setting a new location for the existing mesh in the same blueprint. The way you have it set up there it should fire every time something enters your trigger box (can be anything, characters, any actors, meshes, etc).
The first code should only fire when your character enters it. if DoorsBig is another actor, then it should spawn at the transform. What values do you have you set for the transform?