We have a Zanussi ZDT 6252 dishwasher, 4 years old. All the pale grey plastic parts inside the cavity of the machine have begun to disintegrate eg the plastic is so weak that you can scratch it away with a fingernail. The two plastic nozzles on the lower spray arm sheared away completely, and the wheels on the lower basket have become extremely wobbly and are no longer firmly attached to their supports. This means it is now impossible to glide the basket into the machine. The darker plastic pieces do not seem to be affected. Does anyone else have this problem? Is it possibly a faulty batch of plastic?