FlatList contentContainerStyle -> justifyContent: 'center' causes issues with scrolling
Its not a bug and you're not doing bad, it is the expected behaviour since you're adding explicit flex to the container of the ScrollView's list making it take the overall height of the screen, hence Scrollable only to the screen's content.
You need to use flexGrow instead of flex to solve it
The flex grow factor of a flex item is relative to the size of the other children in the flex-container
<FlatList contentContainerStyle={{flexGrow: 1, justifyContent: 'center'}} //... other props/>