It is probably not a problem with the shoes. These pool cleaners (and automatic pool cleaners in general) often get stuck on the main drain since the implementation on the new anti-entrapment drains. There is a ring that you can buy that goes on the drain. It is designed specifically for preventing pool cleaners from getting caught on the main drain.

http://www.backyardcitypools.com/Automatic-Pool-Cleaners/NE290-Smart-Ring-Drain-Cover.htm