a function os not correctly working on certain subclasses but does work on other subclasses with the same inherited class

So I'm working on a pseudo-RTS style game and have a problem where enemies will spawn in and use navmesh to navigate towards player placed buildings, all buildings types have their own sub-classes and inherit from a single building class. However enemies will not path towards certain building types. They are detecting them and setting them as their target but are not moving towards them. Please, any help would be greatly appreciated.

here is the code which the enemies use to select a target building and move towards it

 GameObject GetClosestBuilding()
     {
         GameObject bestTarget = null;
         float closestDistanceSqr = Mathf.Infinity;
         Vector3 currentPosition = this.transform.position;
 
         GameObject[] objectarray;
         objectarray = GameObject.FindGameObjectsWithTag("Building");
 
         if (objectarray != null)
         {
             foreach(GameObject potentialTarget in objectarray)
             {
                 Vector3 directionToTarget = potentialTarget.transform.position - currentPosition;
                 float dSqrToTarget = directionToTarget.sqrMagnitude;
             //    float priority = dSqrToTarget * potentialTarget.GetComponent<BuildingClass>().lightIntensity;
 
                 if (dSqrToTarget < closestDistanceSqr)
                 {
                     closestDistanceSqr = dSqrToTarget;
                     bestTarget = potentialTarget;
                 }
             }
         }
 
         float attackRangeSquared = (this.attackRange * this.attackRange);
 
         if (closestDistanceSqr <= attackRangeSquared)
         {
             this.inAttackRange = true;
         }
         else
         {
             this.inAttackRange = false;
         }
         return bestTarget;
     }