There could be several problems, but it is mainly air leaking.
In the upper motor house there is a rotation device for distribution of the pressured air, there can be air leaking.
See part Nine of: http://www.jobo.com/jobo_service_ana...etins/b014.htm
The switch between the air of the front and back bottles, located on the left at the back row of bottles, that can be air leaking.
The simplest to check is the switch of air between front and back bottles.
See part Seven of: http://www.jobo.com/jobo_service_ana...etins/b014.htm
Take it apart and put a little bit of grease on the rubber O rings.
Or if you do not use the back bottles, connect the incoming air hoses directly to the air hoses that connect to the front bottles. (but let the switch there, otherwise an error will occur because of an electrical switch in the air switch)
Fix the air leaks and you will have full quantity of chemicals.