Hi @Anonymous,
Does your app run well within your web browser?
I have made a test on my side, and don't have the issue that you mentioned.
Please take a try to add the following formula within the OnSelect property of the "Navigate" button in your Main Screen (click "Navigate" button to navigate to your current screen where the issue occurs😞
Refresh('YourDataSource')
Also please check if the version of PowerApps Mobile App in your iOS device is the latest version, if not, please upgrade it into the latest version, try your app again, check if the issue is solved.
In addition, please take a try to turn off the "Improved app rendering (final validation)" option within Advanced settings of App settings of your app, then re-publish your app, check if the issue is solved.
If the issue still exists, please consider take a try to re-create a new app based on your data source, then run it again, check if the issue still exists.
Best regards,