I've come across a bug related to with multiple page lists. My conference organizer contacted me to say that he could login as a certain user and, after clicking on the registration link, he could see that she had successfully registered for the conference. However, her name did not appear on the list of registrants. The number of items to display on each page was set at the default value of 25. When I took a look at these pages - we had 59 registrants at the time - there were several registrants missing and others appeared twice. Also, it did list the correct number of registrants.
When I checked on my other conference, the number of items to display on each page was set to 0. Not sure why, as I don't remember doing that myself. This causes all of the registrants to be listed on one page. So, I changed this to 0 for the first conference and now the registrant listing is accurate.