My new Dyna-Glo heater won't stay consistently lit. How can I fix it?

The first time I installed this heater in a house it worked perfectly. It never went out unless we turned it off. Two months later I moved and installed it in my new house and now it either stays on for hours like before or turns off every couple minutes depending on its mood. It has the exact same set up in both houses. I’ve tried the typical remedies: The thermocouple is positioned properly… not that it can be adjusted anyways, I’ve cleaned it dozens of times, the pilot is a crisp, blue flame that hits the thermocouple perfectly, the propane tanks are full. Why would it sometimes stay on forever and other times turn off every few minutes?! So frustrating.

Model: BF30DTDG-4 30,000 BTU Dual-Fuel (Propane) Vent-Free Convection Wall Heater