Your boiler is temporarily heating the internal tank to ensure hot water is ready for use, which is a normal operating status rather than a fault.

domestic hot water cycling mode active

What causes this fault?

This status occurs when the boiler detects that the temperature in the integrated hot water storage tank has dropped below the required level. The boiler temporarily stops circulating heat to your radiators to focus all its energy on reheating the internal cylinder. Once the water inside the tank reaches the correct temperature, the boiler will automatically return to its normal heating schedule.