The central spout dispensing unit is not correctly fitted or is wrongly assembled.
Remove and dismantle the parts of the central spout. Reassemble the parts in the right order and reinsert them.
Proceed as follows:
Carefully pull the stainless steel cover forward and off.
Pull the dispensing unit forward to remove it.
Twist off the upper section with the holder for the milk pipework. Pull the component off.
Then pull the Y-shaped piece off.
Remove the spouts .
Fit the dispensing unit back together as follows:
Push the spouts firmly back onto the dispensing unit.
Refit the Y-shaped piece .
Refit the upper section with the holder for the milk pipework. Turn the component.
Refit the dispensing unit in the central spout.
Refit the stainless steel cover.