If you create a View using a View block on one page, and then insert a View block on another page (or template) that uses the existing View, not all of the settings and styles are used by the second View.
Note that when you use an existing View in a View block you have the choice of editing the original View or editing a copy. If you don’t choose either then by default the block refers to the original View. If you choose to edit a copy then a duplicate of the View is created, and can be edited independently of the original View.
The problem with missing styles occurs in the case of editing the original View (the default).