I have a QuadraFire 1200i (fireplace insert) giving me trouble. Seems to light and burn perfectly fine, but once it goes out, it won't come back on with thermostat. I have to force it back on with reset button. I've given it a thorough cleanout, tested the thermocouple wire with a multimeter, checked connections. I don't want throw a control box ($$$) at it just to see. How can I test/troubleshoot?