The water tank is empty. The stirrer is on. The pressure setting on the agitator control unit is too low: Dirt in the water pump: Misalignment of the pump shaft
Add water. Turn off the stirrer. Check and adjust the pressure setting according to the technical data sheet. Clean the pressure relief valve. To do this, contact the company's service department to disassemble and clean the water pump. See manufacturer's manual. Loosen the coupling and align the shaft.