You Can Downgrade
If you decide you've had enough of the July Android 7.1.2 build and its performance you can try dropping back down to an older version of Android to see if that improves performance.
If you’re unfamiliar with how the Android downgrade process for Nexus devices, take a look at this guide courtesy of the Nexus Help Forums.
The guide will walk you through the most important things you need to know about flashing your Nexus 5X to an older version of Android.
You'll want to be very careful downgrading as it could have unintended consequences. Make sure you're comfortable with the overall process before making your move.
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