we had a simular problem with a customers machine on thursday , does yours also lock the ball in and not return it till the next ball starts ?   
check the membrane   , we have these on order as of yesterday with our next load of Stern parts , if there is a small break  this should be the problem ..


yea guys  I am doing some repairs now .. even with 3 full time techs  ( plus Damien) I am doing service calls and small fixes