A method for detecting an operating state of an ejection unit during the printing of an object of a print job comprising one or more objects, wherein the ejection unit is arranged to eject droplets of a liquid and comprises a plurality of nozzles, a liquid duct connected to the nozzle, and an electro-mechanical transducer arranged to create an acoustic pressure wave in the liquid in the duct, the method comprising the steps of: a. actuating the electro-mechanical transducer to generate a pressure wave in the liquid; b. sensing a residual pressure wave in the liquid; c. generating at least one parameter based upon the sensed residual pressure wave; d. determining by comparing the at least one parameter generated in step c. with at least one threshold, whether the ejection unit is in an operative state or in a malfunctioning state; e. ejecting droplets of liquid from the plurality of nozzles onto the recording medium in accordance with the print job; f. scanning a location of the recording medium onto which droplets of liquid from the plurality of nozzles have been ejected, thereby providing a scanned image, wherein scanning a location of the recording medium is performed every one or more objects of the print job; g. analyzing the scanned image of step f. to determine whether the ejection unit is in an operative state or in a malfunctioning state; h. if the determination of step d. and the determination of step g. do not give the same result, letting the second one prevail and providing feedback about the determined state of the ejection unit to be taken into account in step d. during the printing of the subsequent objects of the print job, wherein providing feedback comprises modifying the at least one threshold in step d. for use in further comparisons; i. repeating steps from a. to h. until the last object of the print job. a. actuating the electro-mechanical transducer to generate a pressure wave in the liquid; b. sensing a residual pressure wave in the liquid; c. generating at least one parameter based upon the sensed residual pressure wave; d. determining by comparing the at least one parameter generated in step c. with at least one threshold, whether the ejection unit is in an operative state or in a malfunctioning state; e. ejecting droplets of liquid from the plurality of nozzles onto the recording medium in accordance with the print job; f. scanning a location of the recording medium onto which droplets of liquid from the plurality of nozzles have been ejected, thereby providing a scanned image, wherein scanning a location of the recording medium is performed every one or more objects of the print job; g. analyzing the scanned image of step f. to determine whether the ejection unit is in an operative state or in a malfunctioning state; h. if the determination of step d. and the determination of step g. do not give the same result, letting the second one prevail and providing feedback about the determined state of the ejection unit to be taken into account in step d. during the printing of the subsequent objects of the print job, wherein providing feedback comprises modifying the at least one threshold in step d. for use in further comparisons; i. repeating steps from a. to h. until the last object of the print job.