Both the Wreck_UH1Y and the Wreck_Mi8_Crashed are spawning particles in the constructor but dont clean it up in destructor or via eedelete causing the particles to still be there when the event is cleaned up.

Both examples here:
class Wreck_Mi8_Crashed extends CrashBase
{
void Wreck_Mi8_Crashed()
{

		if ( !GetGame().IsDedicatedServer() )
		{
			m_ParticleEfx = ParticleManager.GetInstance().PlayOnObject(ParticleList.SMOKING_HELI_WRECK, this, Vector(2, 0, -5));
		}

}
}

class Wreck_UH1Y extends CrashBase
{
void Wreck_UH1Y()
{

		if ( !GetGame().IsDedicatedServer() )
		{
			m_ParticleEfx = ParticleManager.GetInstance().PlayOnObject(ParticleList.SMOKING_HELI_WRECK, this, Vector(-0.5, 0, -1.0));
		}

}
}

additionally, we got this in the crashbase:

override void EEDelete(EntityAI parent)
{

		if ( !GetGame().IsDedicatedServer() )
		{
			if ( m_ParticleEfx )
				m_ParticleEfx.Stop();
		}

}
but it doesnt seem to get the particles parent at all