Hi,I have a tricity bendix DH090 dishwasher and i have just replaced the lower spray arm nozzle.When I rotate the arm though it is dragging on the outside rim of the filter plate and seems to need raising slightly.Can you tell me if there is usually some kind of washer or seal that fits into the centre hole of the filter plate that the stem of the spray arm then fits onto? I wondered if it may have perished.I have checked to see if the plate is warped but it fits flat all around and that the nozzle is fitted correctly.Or maybe there is usually a washer that is missing on the stem somewhere . It only needs raising a fraction to rotate correctly. I can see you have several o rings for this model but im unsure if any of them are what im looking for