Navien combi does Startup/Post Purge cycle few times a day when there is no call for heat/hot water

I am homeowner that recently had a Navien NCB 240/110H professionally installed. I work at home and the unit is in a closet next to my desk, so I hear everything it is doing. It's summer and the thermostats are switched off, and I can hear water running in case anyone using hot water. Several time each day I can hear it come on when it is not needed. When I check the Status on the panel, there is no flame, but it cycles between Startup and Post Purge for approximately 5 minutes. I called Navien tech support and reported it and they said it is normal and it is doing a calibration. They couldn't provide me details of why it does it so often. Since then I have noticed when it is doing this, that there is a gas smell coming from the exhaust vent outside, which certainly does not seem normal to me. Anyone heard of this?