Why doesn't my Tricity Bendix DH090 dishwasher drain all the water out?

I have a Tricity Bendix DH090 dishwasher and it has been no problem. But lately it has not been draining properly, leaving enough water behind to cover the filters, sometimes even more. There were no warning signs or indications this was about to happen. I have checked the outlet pipe for blockages or clogging (There's None); no kinks and no squashed pipes, and apart from pulling it out in order to check these things, the dishwasher has not been moved since installation.
I am at a loss, so suggestions for sorting it or which parts might need replacing,please... anyone? x