When spawning object the object is its normal size for a split second

Basically I have a monster spawner and Im trying to spawn monsters from it.
And currently I have 1 normal monster prefab, which I use for instantiating the monsters. I also used this normal monster prefab and made an original prefab copy and changed the size to be bigger and the color to be green. However as soon as the boss monsters spawns it is the 2x size for like 0.01 second, then it goes back to the same size as normal ones. However the color is still green.
Could anyone explain me why is this happening and how to solve it?
Code:

[SerializeField] private float spawnInterval = 3.5f;
public Transform spawnPoint;
public GameObject startingMonster;
public GameObject bossMonster;

private int counter=1;
private int counter2=1;
void Start()
{

StartCoroutine(spawnMonster(spawnInterval,startingMonster));
}

/
void Update()
{

}
private IEnumerator spawnMonster(float interval,GameObject enemy)
{

yield return new WaitForSeconds(interval);

GameObject newEnemy =Instantiate(enemy,spawnPoint.position,spawnPoint.rotation);
if(counter==5)
{

GameObject boss =Instantiate(bossMonster,spawnPoint.position,spawnPoint.rotation);

}
if(counter==5)
{

Enemy en =newEnemy.GetComponent();
en.IncreaseHealthAndDamageAndSpeed(0,counter250,counter20.5f);

counter=0;
counter2++;

}

counter++;
StartCoroutine(spawnMonster(interval,enemy));
}

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Where are you scaling these things?

Are you spawning two objects in the same spot? The code above kinda looks like you might be but hard to say without formatting.

Technically yes. Im spawning 2 objects at the same time. However that should not be a problem since they dont interact with each other

I am scaling it in the unity editor. I tried everything even with the localscale code in a script, nothing works. I tried running the game, pausing it and scaling the object but as soon as I hit play again it just goes back to the original size. Also the scale says: x=-1 and y=1

What other components are on those instantiated objects? Any scrips? Any of them doing anything to the scale? Something is overwriting your manual changes after all.

Perhaps an animation? Even a default empty one-frame one?