I've been trying to debug this intermittent problem. Wondering if anyone has experience or can give guidance because I'm all out of ideas. Enviro M55 insert. Installed for 3 years. Had this problem last season too. Ecobee Smart SI wireless thermostat. Controls both the Stove (stage 1) and Oil furnace (Stage 2) Ecobee controls two 24v relays that are connect to stove & furnace. There's three modes on the M55, Manual / Auto / Auto on-off. I generally use Auto which will run the stove on the lowest setting until heat is call for. Everything will work as expected but then the M55 seems to stop responding to the t-stat. It will run on the lowest setting. I have tested the wiring all the way up to the back of the stove and it's OK. An interesting thing I've discovered is this; If heat is being called for and the M55 is in Auto but running on the lowest setting. If I switch the M55 mode to manual it will switch from the lowest setting to whatever heat output setting it's set to (expected). Now if I switch back to Auto - It will obey the t-stat. This is reproducible 100% of the time which would cast some doubt on the problem being intermittent faulty control board in the stove. It seems like that might mean an intermittent fault in the control board, but I want to check in to see if anyone has experience with this issue. thanks!