Broken coverslips are not detected – what can I do? FAQ Report A:There are two possible causes –the coverslip sensor or the suction cups require cleaning or the suction cups are deformed If the coverslip sensor (located between the red suction cups) appears dirty, clean it with a tissue moistened with xylene (work carefully - suction cups must not come into contact with xylene). For a more thorough cleaning job, the sensor can also be removed (details on how to carry out this procedure are available from your Leica service representative). If the suction cups are dirty, clean them with a tissue. If the suction cups are deformed (possibly caused by exposure to xylene), replace them.