I am trying to clean my Miele Inspira G2180Vi. As per P. 47 of the Instructions, I have pulled out the non return valve. In checking the propellor, it does not spin freely, sort of clicks at one point, but there is nothing caught under it. In other words, I can spin it in both directions but it won't go freely all the way round. Is this normal? Thanks, Mary Pike 250 746-9209