please provide more information for this, such as screenshots from the autoindex and the configuration for the index fields and lists you are talking about.
To me, it sounds like the default select list (which updates automatically) is used in the workflow designer tasks, whereas in the webclient you use static/fixed lists for your dialogs.
If this is not the case, we need more technical details to be of help.
Greetings from Germany,
Simon H. Hellmann