Its gonna get cold soon

A gentleman from the Truck camper FB page found the manual for me online. I was just working on it and trying different scenarios. One thing I find odd is If I go though the steps of lighting it. I have it running, heats blowing. I turn the therm down and I hear the burner shut down and it runs for about a min to cool down the heat exchanger. Once the fan shuts down if I turn the therm back up within a few seconds it fires right back up and works fine. I can do this over and over again. Now, if I turn the therm down, let the heater sit for a few minutes and then turn it back up the blower will come on but the burner wont light. I tried this a few times and finally caught a clicking noise coming from the heater and I'm assuming at that point is when it becomes non functioning. I dont know if its the gas valve shutting the pilot off or if the delay module inside is clicking and shutting the pilot down.Once again I dont really even know if the pilot is shutting down because there's no view point to see it. I read the pilot section of the manual and I dont totally understand it. It makes me wonder if I could of caused this issue when I rebuilt the side of the camper. I had the exhaust plate off and was fiddling with the extension they are referring to cutting down. I dont even understand what that does for it. Any idea?