Possible cause:
Scale in the drip coffee unit.
Do you need descaler? Delonghi's EcoDecalk has been specifically designed with your machine in mind. Using this descaler regularly will prolong the lifespan of your machine and keep it running at optimal performance.
De'Longhi Coffee Machine Descaler EcoDecalk 500ml Best Value Pack (delonghi.com)
Follow the step-by-step guide:
Follow the instructions given on the packaging of the descaling product.
Then turn the coffee machine off.
Then turn the coffee machine off.