If a technician observes wavering flames in one corner of the burner after startup, what could this indicate?

Wavering flames in one corner of the burner after startup typically indicate poor combustion, which can be related to issues with airflow or gas flow. A faulty heat exchanger can lead to improper combustion characteristics due to restricted airflow or uneven heating, potentially causing the flames to appear unstable or wavering.

While other options address potential issues with gas supply and airflow, the heat exchanger's role in managing air distribution and maintaining the appropriate environment for combustion directly connects to the observation of wavering flames. If the heat exchanger is compromised, it can disrupt the balance needed for consistent flame behavior, leading to the wavering effect noted by the technician.