Good afternoon everyone. I'm having a problem with my furnace. I have a Crossroads Rezerve 31sb, 2016. It has the Atwood furnace in it. It started on me last time out, but seems to be worse now. The furnace kicks on, fan/ blower runs, the combustion chamber lights and heats for about 10 seconds and shuts off. 20 seconds later it lights again and stays on for another 10 seconds again. This goes on until it gets to temperature. I believe it use to stay lit and heating for the entire duration until it brought the camper to temp. Both propane tanks are full, the blower continues blowing air the entire time. The thermostat is set to 75 degrees, doesn't matter if blower switch is set to on or auto. I'm sure someone in this forum family has ideas or thoughts. Thank you all in advance. I'm wondering if a blockage in intake or exhaust? The exhaust vent is siliconed to side of camper and not where I can cut it to remove to check inside. No access to internal furnace inside camper, other than removing wooden vents under refrigerator. It's self contained under there.