Melitta ci 970-205 sometimes does not draw water

Hello,

we bought a Melitta CI 970-205 in March 2017. For quite some time now, very little or no coffee has been coming out of the designated nozzle. Sometimes nothing at all, sometimes a little, sometimes quite normal. When I take out the brewing unit I can press a plastic rod at the bottom, which makes the whole unit move inside (sorry for the inappropriate labelling). Most of the time it works again a few times. Before that I cannot move anything inside the brewing unit. We clean the machine every Friday (office machine) and always carry out the maintenance programs when the machine shows it. Does anyone have any idea what this could be? Have read here partly from any valves. But I don't really know what to do with them.

kind regardsAndreas