Stuck on this one. – Miele integrated dishwasher wont stop!

Sorry, I didn’t take note of the model when I went out to it.

Its a Miele fully integrated dishwasher about 11 years old.
Customer told me over the phone that he had been messing about with the latch hook as the door wouldnt close easily. As a result, he had managed to click the lock over and couldn’t return it.
Nice easy job I thought, so I turned up and returned the latch with a small screwdriver. I noticed the dishwasher had shunted back into place slightly which was the reason he was having problems closing the door. I brought it forward 10mm and presumed job was done. Charged them, everyone happy.
Got a call the day after saying it was still running after 4 hours and wouldnt fill up. Flood protection activated I thought.
Returned today and to no supprise the base was full of water.
I ran it with the front plinth panel off and noticed water running out of a plastic breather/drain tube at the front left corner of the machine.
I opened the door and took a look inside and noticed the sump filter wasnt seated correctly restricting the lower spray arm, holding it in a position so it was jetting water straight to the lower door seal which i thought was causing the problem. (The customer admitted to this.) Put the sump filter right, dried things up and tested again. Everything seemed ok, put the cover back on and thought I had sorted it.
No further charge, all part of the job. Got a call today 4 hours later saying that it still not working after 4 hours.
Arrghh.. I dont really have any experience with Miele stuff, begining to wish I had just told them I dont touch it but it’s booked in for uplift on Monday morning to spend some time in my workshop.
I noticed the PC light was on, but the customer informed me this was the salt indicator which makes sence as it has the salt symbol next to PC. I thought this was a service light indicating a PC requirement.
Ohh someone throw some light on this for me please..
Many thanks,
Rob.