Why does my D7 User view only display 6 results in Block View, but all results in Page view?
A good way to start understanding what happens is to turn on the Show the SQL query option  in the basic view settings under admin/structure/views/settings. You can then copy-paste the generated query into your database application and check if the query catches all expected results. If yes, then the problem most probably happens during the rendering of the results, maybe a custom views block template (check the theme overrides for the views display)? If no, then there is probably something wrong with the query itself, which could be either some kind of filtering, or maybe a contrib module that alters the query from code.