If your tapping or typing test steps consistently fail on particular iOS devices but pass on others, the problem may be scaling of the app display for certain device form factors. If an appropriate launch screen image is not available for your app, it will be run in a scaled or compatibility mode. Apps running in scaled or compatibility mode can cause incorrect coordinate calculations and result in test failures when tapping or entering text.

If your tests consistently work on one or more device models but fail on certain other models while tapping or entering text this could be the issue. For example, your tests work on an iPhone 7 but have issues tapping or entering text on the iPhone 7 Plus, or only fail on the iPhone X, or on some or all iPads. The underlying issue to look for is that the app is not running in native resolution on the failing device(s) but is running in native resolution on the devices that pass the tests.

To fix this problem your app will need to run in native resolution. To do that, make sure to include all required static launch screen images or use a storyboard for your launch screen. You will also need the appropriate app icon sizes. 

See the references below for more information.

References:
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​Static Launch Screen Images
​It’s best to use an Xcode storyboard for your launch screen, but you can provide a set of static images if necessary. Create static images in different sizes for different devices, and be sure to include the status bar region.
​https://developer.apple.com/ios/human-interface-guidelines/icons-and-images/launch-screen/

App Icon Sizes
​Every app must supply small icons for use on the Home screen and throughout the system once your app is installed, as well as a larger icon for display in the App Store.
​https://developer.apple.com/ios/human-interface-guidelines/icons-and-images/app-icon/
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