Ariston A1635 - conditioner tray not draining?

we have had our Ariston A1635 for 5 years now with no problems at all. The last 2 weeks we have noticed the tray where the conditioner goes is not emptying and is filling with water. Ever time we use it we're having to take the excess water out of the tray to add the conditioner and when the wash has stopped you open the tray and the conditioner has gone and been replaced again with water. The water does not over flow, its just a pain as we have to keep putting kitchen towel in the tray to soak up the water.
Any idea what the problem is, and how we can fix it? Thanks