SMEG type 10045 DWF 66SS

My daughter has recently moved into a flat, which contains a rather unloved and rank smelling SMEG dishwasher. Having removed aeons of congealed fat from the filter and obtained instructions from the web, I have run the hottest programme, having first dumped the contents of a packet of washing soda into it. When the cycle starts it appears to run normally, however after a bit, it sounds as if the the washing cycle has become intermittent in that it only flushes round for a few seconds then cuts out, then restarts and the same things happens. If the door is released,closed and restarted, it works normally again for bit, then starts re-cycling again. It appears very slowly to be improving, but has not yet cleared.

The washer is not draining properly at the end of the cycle however – the level remaining just above the top of the filter. There don’t appear to be any error codes however! Any suggestions? – main priority is to get it to drain properly!