there are 2000 of these machines on base. some keeps having helix and pulley issues, . the machines goes into spin and makes a terrible noise, finding the helix to be worn down so that the pulley rides up the helix and insteadof staying into spin it falls off making this huge noise. any idea whats causing this? i have changed both helix andpulley and last for about 2 months and happens again. any ideas?