Differentials in humidity in a cabinet

[markem]

Unless the cabinet is 15' tall (that's approximately 5 metres ), then I'd say it is unusual and probably indicates an area where airflow is restricted. Playing a bit of tetris to create vertical gaps for air movement may help as may putting a fan at the bottom in that location and having it blow upwards. If the differential stays after adjustment, then I'd say that you are in for rotating beads through that area in the long haul.