I have a Monessen DEB20 ventless, natural gas, millivolt, remote control fireplace. The remote control recently quit working. I replaced the remote and the remote receiver to no avail. The flame also started going out after 20 minutes of good use. The pilot light never goes out. I replaced the ODS Pilot assembly to no avail. The fireplace lights using manual controls and works fine until there’s a clicking sound and the fire extinguishes. I’ve eliminated the remote control and pilot/thermocoupler as problems. What’s next?