We have a 10ish year old natural gas Heatilator IPI fireplace (Novus series I believe). All this past winter it's gotten increasingly difficult to start. When you first try (thermostat calls for it to start), you hear 3-4 short clicks in the fireplace but nothing happens. I'll have to repeat this several times (anywhere from a few to10-20 if I'm determined) to finally get it to start, Weirdly once it's start it can stop and restart with zero issues until it's left off for a few hours then gets difficult again, almost as if it works fine when everything inside it is warm/hot but struggles otherwise. I had it cleaned/serviced mid winter and the tech checked several things and cleaned everything up and of course worked when they were there because it had been warm/hot inside, but trying it later that night the issue returned. What would cause the fireplace to struggle to get that first light going, but be fine after on/off until it cools down again?