Your boiler thinks it still sees a flame even though it has commanded the gas to turn off, which is a safety conflict.

False flame error (Flame detected after burner stop) or Gas valve EV2 leak test failed

What causes this fault?

This fault occurs when the boiler's internal sensors continue to detect a flame even after the system has commanded the gas valve to close. This is usually caused by a gas valve that is physically stuck open and leaking fuel, or a faulty control board that is misinterpreting electrical signals from the flame sensor.