Ok what happens is the small plastic tabs break which hold the feed pipe in at the back so that's why its popping out all the time.
What you need to do to fix this is remove the sieve filter cover. If you remove the filter mesh in the base you will see this part. Theres about 4 screws holding it on.
Click here for the part
Then with the new sieve filter cover fitted you can then clip the feed tube and that will keep in in place and cure the fault.
Its quite common on these dishwasher for this part to break and cause the fault you have. Ive replaced loads of them in the past.
If you need anymore info just get back to me.
Thanks for your advice.I run a small servicing business and will be using you more often,regards Ian