My Defy Automaid DAW285 only works when you put in a small load of washing

Sometimes even with a small load it does not go into spin cycle but if I turn the pulley - like almost starting it - it goes into the spin cycle. I can only wash 2 shirts and a few socks at a time and it works fine to the end of the spin cycle, but I cannot even wash one towel or add more items then the drum won't go round. Have replaced the belt and cleaned the filter. But is still having the same problem.