All people-categories (except Unsourced Profiles) tend to lose people where an LNAB crosses a page break. The more members there are that have the same LNAB, the bigger the problem.
It seems to happen because the paging system thinks the list is sorted in order of WikiTree-ID.
1 - One thing that seems like it ought to work, but who knows, would be to apply the category to each profile using
Ideally this needs a template.
2 - Another way is to break up the list into smaller categories, less than 200 people. There's an official scheme for doing it by place - the format would be [[Category:Franklin County, Pennsylvania, Chadwick Name Study]]. Or they could be split by first name "Chadwick, A" "Chadwick, B" etc. Or by immigrant, if you can separate them into tribes. Or whatever.
3 - The Unsourced Profiles category works round it by being sorted by ID instead of name. This jumbles the first names but makes the paging work.