Spin fault on Zanussi ZWF1221W?

I have a very obscure fault on my ZWF1221W W Machine. Intermittently it won't go into full spin. It drains ok, starts to spin at around 900 rpm, it then continues at this low rate whilst intermittently flashing all the delay start LED's and the wash LED. It will do this for the full spin cycle and then end. At the end there is no fault indication on the LED's to show there has been a problem, but the clothes are soaking wet.