screenwasher rear door problem Peugeot Partner

I have a problem with the screen washer of the rear door, left hand side. At first I thought it would be a simple job (cleaning nozzle with a pin), but I can't seem to get it fixed. The other rear door washer works OK and the front washers also work OK. I suspect I have to look inside the left rear door itself to find leak or the tube has slided off somewhere. How can I remove the panel inside the door? Can I just force the knobs with a screwdriver to make the panel come off?