Bosch Dishwasher – Low water pressure in spray arms

Model Bosch SRS 4002 GB/01

Our dishwasher has stopped cleaning, it has worked OK for years but one evening the dishes came out still covered in food, the detergent tablet had not dissolved either.
I jammed the door mech and ran the machine, there was a dribble of water out of the bottom arm and nothing from the top.

What I’ve done so far.
1: I’ve had the arms and the associated tubing out and washed them through with a hose.
2: I’ve cleaned all the filters inside the casing and cleaned out the sump.
3: I’ve pulled the sides off and cleaned all the tubing and the small transparent hose on the left side of the machine.

The above three cases resulted in virtually no debris being removed (we rinse the crockery under a tap before it goes in the machine).

When washing the water level in the machine is just over the level of the sump.
Would this be correct ?
When on the wash cycle, with no arms fitted the water pressure lifts a jet of water approx one to two inches high. If I tap the machine around the main pump area we can sometimes improve this to four inches ! !
Does this make any sense ?

With the machine unplugged I put my finger in the sump and felt inside the main pump. There seemed to be an inner and an outer part of the pump which spin independently (i.e. if I hold the shaft of the motor from the outside I can turn the outer part of the pump from inside the pump
Is this correct ?

The water only feels lukewarm, would this be due to low pressure ?

Any other idea’s / suggestions would be greatly appreciated.

Thanks.