iOS modal causing weird layout animation glitches, with new arch

Description

Hi there,

There are some weird glitches animations happening when using the presentation's modal. I'm using expo-router, but I'm assuming the issue is coming from upstream with react-native-screens.

Issues happens with presentation modal, pageSheet or formSheet values.

Repro uses a FlatList, but I've seen the issue happening with a ScrollView as well.

https://github.com/user-attachments/assets/9a8dcee8-e306-4234-a651-d78606054895

I've seen many open issues regarding the Modal but couldn't find anything that's too similar to this one, so opening a new issue.

Steps to reproduce

1. git clone git@github.com:jeremybarbet/unistyles-sandbox.git
2. git checkout repro/modal
3. yarn install, yarn prebuild and yarn ios
4. Press "Open modal" and you will see something weird happening. If it doesn't happen, reload the screen + press "Open modal" again, until the glitches appear

Snack or a link to a repository

https://github.com/jeremybarbet/unistyles-sandbox.git

Screens version

4.11.1

React Native version

0.79.4

Platforms

iOS

JavaScript runtime

Hermes

Workflow

Expo managed workflow

Architecture

Fabric (New Architecture)

Build type

Debug mode

Device

iOS simulator

Device model

No response

Acknowledgements

Yes

Clone jeremybarbet/unistyles-sandbox, check out repro/modal, install dependencies, run yarn prebuild and yarn ios, then use the Open modal entry point to reproduce the glitches. Compare behavior for modal, pageSheet, and formSheet with FlatList or ScrollView on iOS Fabric; done means identifying a reproducible upstream cause and confirming the animation no longer glitches.