If items are being skipped then it makes sense that you would see 99's as that is the default value for missing values and skipped items. It sounds like you are not expecting any (or some) of these items to be skipped though. If that's the case, please attach or email us a copy of your experiment folder--complete with the exp, que and data folder and I'll check it out. Be sure to zip the folder before attaching it (as opposed to attaching several separate files).