There is another screen , it is on the birne piston assembly, it is a pain to get to but can be worked on.
How is the drain line pressure?
Have you removed the cover to make sure that the brine piston is moving in and out?
It could be that one of the o rings on the brine piston is bad and the assembly will need to be replace.
Water on top of the motor?
Can you work with a parts break down?