Hygena Dishwasher APL8212 not draining properly

This one had a leak from the bottom corners of the door.
Customer replaced lower spray arm and says it “no longer leaks, but there is a lot of water left inside at the end of a cycle”.

Upon investigation, when it is draining, there is a lot of water coming back up through the lower spray arm and also out of the covered two apertures pictured here with the cover removed:

(edit – i tried to paste the link for the picture in, but it may not have worked, so here’s the url: http://www.flickr.com/photos/87098153@N … hotostream )
There is a rubber flapper valve just sitting on top of the hole nearest the front of the machine – you can pick it up with your fingers – it is not attached to anything.
I’m wondering if this is the cause of the problem, or if this is how it should be and the cause is elsewhere.
Any pointers gratefully accepted.

Many thanks,
Pigpen.