Assigning instantiated object assigns other object instead

Hi. I have this following piece of code,

                     if (up == null)
                     {
                         up = Instantiate(PlaceholderPrefab, transform.position + Vector3.up, Quaternion.identity);
                         AdjacentRooms++;
                     }

but instead of instantiating a new object and assigning it to the variable up, it takes a random object in the general area that it should be instantiated and assigns that to the variable instead.

Any idea why?