saniflo - Sanivite?

Bought my sanivite 3 years ago, just got round to installing it (cellar). I only have the washing machine connected, worked fine for the first two washes, on the 3rd wash it worked then stopped and flooded my cellar, then started then stopped. Cellar has now been flooded 3 times, What can it be and can i fix it?
Cheers for any help

Paul
November 2013