After closer inspection, the fan turns on about 2-3 minutes after shutting off at the end of a normal cycle. Apparently, the system is not trying to restart the burner since it thinks it is still in the shut down phase. I could not get a response from Airstream so I called Atwood. They said the circuit board may be wet or has corroded and needs to be replaced. Atwood asked me to open the furnace cover and check the circuit board. When I opened it, I found an unused rivet lying across the circuit board obviously creating a short.
So far, the system seems to be working correctly.