Prepending items to the data prop changes firstItem

Is this a bug report, a feature request, or a question?

Question and/or a bug report.

Have you followed the required steps before opening a bug report?

• I have read the guidelines regarding bug report.
• [x ] I have reviewed the documentation in its entirety, including the dedicated documentations 📚.
• [x ] I have searched for existing issues and made sure that the problem hasn't already been reported.
• [ x] I am using the latest plugin version.
• [ x] I am following the issue template closely in order to produce a useful bug report.

Have you made sure that it wasn't a React Native bug?

I believe so.

Is the bug specific to iOS or Android? Or can it be reproduced on both platforms?

Only testing in iOS at the moment

Is the bug reproductible in a production environment (not a debug one)?

Have not tried in production.

Environment

React: 16.8.3
React native: 0.59.5
react-native-snap-carousel: 3.7.5

Expected Behavior

For performance with a large data list I am basically doing what is described in this issue: https://github.com/archriss/react-native-snap-carousel/issues/384

I am managing a smaller list specifically for in the data prop. I am handling infinite scrolling/pagination manually by detecting the start and end indexes in onBeforeSnapToItem. I want to be able to land in the middle of a list of items and as I swipe right AND left, new items will be loaded into the list in regards to the direction I was swiping (prepending or appending)

Actual Behavior

It works fine for when you are swiping forward (or 'right') and you reach the end. I append the new items in the list and everything is okay.

The issue is when you swipe backwards (or left) and load some more data. I prepend the data to the list and the firstItem is completely lost and the carousel renders the very first item in the list, which is incorrect. The firstItem prop should remain unchanged when prepending data to the list.

Reproducible Demo

I will provide a reproducible demo if needed. I wanted to ask to see if you knew a quick solution or if this was a limitation of FlatList.

Start with the Carousel data, firstItem, and onBeforeSnapToItem behavior described in the report, then inspect how the underlying FlatList responds when items are prepended. Reproduce the case on iOS with react-native-snap-carousel 3.7.5, beginning from a middle item and loading items while swiping backward. Done means the carousel preserves the selected firstItem after prepending while existing forward pagination still works.