Delonghi Dedica problem

[ianb]

Hi guys, I've had the Dedica for about 3-4 years with no problems. However, it now won't pull a shot with the double basket in, but works fine with the single basket. Nothing has changed with the beans I use, the grind and the machine was last descaled about 1 month ago and is in clean condition. I have even replaced the double basket in case there was some invisible blockage in the hole in the base.

So I've replaced the pump and the pressure valve as I can't see anything else that would affect this, but I still have exactly the same issue. I'm out of ideas so if anyone has any thoughts I'd really appreciate it. Thanks, Ian