Decal Actor need to adjust rotation after spawning

[EvangelionZero]

I am trying to spawn Decal Actor in level by using SpawnActor<>() function (somehow UGameplayStatics::SpawnDecalAtLocation didn’t work).

and this is my code:

---

void ASplashTestBall::NotifyHit(class UPrimitiveComponent* MyComp, class AActor* Other, class UPrimitiveComponent* OtherComp, bool bSelfMoved, FVector HitLocation, FVector HitNormal, FVector NormalImpulse, const FHitResult& Hit)
{
	Super::NotifyHit(MyComp, Other, OtherComp, bSelfMoved, HitLocation, HitNormal, NormalImpulse, Hit);

	if (!bCanJump)
	{
		// Set up Transform
		FVector Size = { FMath::RandRange(1.f, 2.f), FMath::RandRange(1.f, 2.f), FMath::RandRange(1.f, 2.f) };
		FVector Location = Hit.ImpactPoint + Hit.ImpactNormal * 40.f;
		FRotator Rotation = (-Hit.Normal).Rotation();
		FTransform Transform(Rotation, Location, Size);

		// Set up Material
		UMaterialInstanceDynamic* SplashDecalMID = UMaterialInstanceDynamic::Create(SplashDecalMaterial, nullptr);
		SplashDecalMID->SetScalarParameterValue(TEXT("Frame"), FMath::Rand() % 6);

		// Spawn Decal Actor
		//UGameplayStatics::SpawnDecalAtLocation(this, SplashDecalMID, Size, Location, Rotation);  // Why not working ???
		ADecalActor* NewDecal = GetWorld()->SpawnActor<ADecalActor>(ADecalActor::StaticClass(), Transform);
		NewDecal->SetDecalMaterial(SplashDecalMID);
		NewDecal->GetDecal()->SetFadeOut(20.f, 5.f);
		NewDecal->SetActorRotation(Rotation);	// I dont know why I need Do it again
		DrawDebugSphere(GetWorld(), Hit.ImpactPoint + Hit.ImpactNormal * 40.f, 19.f, 20.f, FColor::Red, true);
	}

	bCanJump = true;
}

---

with these code, things go well

if I don’t have

NewDecal->SetActorRotation(Rotation)

after spawn, the rotation of Decal Actor looks like be changed by something

Why I need adjust rotation after spawning?
Why SpawnDecalAtLocation didn’t work?
I’ll be so appreciated.