As I mentioned, let's clear the cache on the phone, and the try safe mode. Safe mode will not erase any of your data. This will temporarily disable all downloaded apps, until you reboot the device again. This means any apps that you installed from Google Play, or other sources. This is to see if the camera distortion is being caused by a downloaded app interfering with the device.
Before we get into safe mode, to clear the cache, go to Settings > Storage > touch 'Cached data' > touch 'OK' to clear.
To get into safe mode, have the Nexus 5X's screen on, and unlocked (like on a homescreen). Press and hold the Power button until the power menu comes up (~2-3 seconds). When this does, you should see the option for ‘Power off’. Touch and hold on ‘Power off’ on the screen until another window comes up. This window will tell you about safe mode, so take a moment to read about it. When you’re ready, touch ‘OK’ to reboot.
Test around in safe mode for a while. If the issue still exists, then proceed to the next step. If it doesn’t seem to come back while in safe mode, it’s possible that there’s an installed app that’s causing the problem. It’s hard to say which app it is, so the best way to tell is to start uninstalling the latest installed/updated apps. Reboot into the normal mode (by powering down the device, and then powering it up again), and start uninstalling apps until the camera warp doesn’t seem to be around.
If that doesn't help, then try going to Settings > Apps > Camera > Storage > touch 'Clear data' > touch 'OK' to clear. Try the camera again. If it's still the same, then return to that menu before 'Storage', and touch 'Uninstall updates', if available.
If that all still doesn't work, please let me know, or contact us again!