Common issues that can affect boiler performance include scaling and corrosion, faulty thermostats, improper installation, and inadequate maintenance. Scaling and corrosion can reduce the boiler’s efficiency and lifespan, while faulty thermostats can cause the system to malfunction. Improper installation can lead to safety hazards and reduced performance, while inadequate maintenance can cause the system to break down prematurely. Regular inspections and maintenance can help identify and address these issues before they become major problems.