Your boiler is simply finishing a safety cooling cycle after you have finished using hot water, and there is no cause for concern.

DHWmode:Pump/fanoverrun

What causes this fault?

This status occurs as the boiler completes a safety sequence to confirm that the internal pump is circulating water properly and the fan is operating at the correct speed. It is a normal part of the start-up process where the system verifies all conditions are safe before allowing the burner to ignite. If the code stays on screen too long, it may suggest a slight delay in the pump or fan reaching their required operating levels.