Pressure chamber switch Siemens

Siemens Dishwasher (SE58591/06, 1997 model)

So here’s a challenge…..

I notice when my machine is coming to the end of the cycle, i.e. going from rinse to drying cycle (when running in 55 degrees economy mode) strange things happen.

Occasionaly the rinse water is pumped out and then the water matrix starts to fill up with water. (approx 12 minutes left on timer). When the matrix fills up, the water starts to run into the sump and normally the pressure switch activates and stops after a few seconds, letting the drying cycle finish normally. What occasionally happens is the pressure switch does not activate and the sump fills up full. This means at cycle end, the machine always makes a last pump, seconds before finishing the complete cycle. Sometimes the pump therefore needs to pump out the entire machine leaving nice warm and steamy cutlery… Occasionally the display shows error code F.

I have changed the entire pressure switch which is what confuses me and also cleaned out the tube between switch housing and sump (which was actually not dirty)…

Any ideas??