I leave my MES 30 unplugged when I cold smoke. I just use the AMNPS and yes, I've had problems with it going out during cold smokes. I usually place two half-gallon milk jugs containing frozen water on the 4th rack of the MES which is below whatever I'm cold smoking. I think part of the reason why the AMNPS went out both times I cold smoked was because I picked cold, wet nights when there was a constant drizzle outside.
But--and this is an important but, my friend--the AMNPS still produced more than enough smoke so that the cheeses I had in there turned out a bit oversmoked. The AMNPS did its job. The smoke remained even though I had the top vent wide open.
It's possible the milk jugs blocked some airflow and the coldness emanating from them might have also killed the wood pellets so I'm skipping them next time.