List entries disappeared and sorting difficult as a consequence

@Horst  Unfortunately this is a long-standing bug in the lists system which especially affects large lists.  The lists system is now over 13 years old and is some of the oldest remaining software on IMDb. We are actively working upon its replacement as part of the on-going design and technology migration, which will address the issues.  In the meantime, as we recently wrote here:  If you have access to the IMDb iOS app via an iPhone or iPad, this is best way to manage lists on IMDb. I have hundreds of lists, both private and public, which I manage via our app.   The web interface will improve once it moves to the new technology, but right now the iOS app is the gold standard list implementation Sorry for the inconvenience in the meantime.  We can fix individual cases if you provide the URLs, but please be aware that a single edit can re-break the ordering until the new list software is launched.