[Honor 5X ROMs, Kernels, Recoveries, & Other Develo] FalconFour:
Interesting little bug report here (on 20160827 build with GApps installed via Aroma). I don't know if it's useful to the devs to "submit" a crash report when it happened, but here's the report, and the context of it.

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.android.settings/com.android.settings.bluetooth.BluetoothPairingDialog}: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.bluetooth.BluetoothClass.getDeviceClass()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2450)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2510)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1363)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5461)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.bluetooth.BluetoothClass.getDeviceClass()' on a null object reference
at com.android.settings.bluetooth.BluetoothPairingDialog.createView(BluetoothPairingDialog.java:274)
at com.android.settings.bluetooth.BluetoothPairingDialog.createConfirmationDialog(BluetoothPairingDialog.java:328)
at com.android.settings.bluetooth.BluetoothPairingDialog.onCreate(BluetoothPairingDialog.java:136)
at android.app.Activity.performCreate(Activity.java:6251)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2403)
... 9 more

Seemingly at random today, my phone kept waking up with a generic notification sound, and the notification appeared: "Settings / Content hidden". Strange. So I tapped the notification and unlocked the phone. That's when I saw "Settings has stopped working" (or, eh, whatever the wording is today). OK, or Report. I went for Report.

Once I read over the error, it pointed to a problem with Bluetooth. For some reason, though I never disabled it (I always always leave it on), Bluetooth was switched off. So I switched it back on.

Almost immediately, I got a notification that my Android Wear watch (Samsung Gear Live) wanted to pair with the phone. Strange, it was already paired (by design). So, the OS lost all its Bluetooth pairings. So I allowed it to pair again.

And that was the end of the mysterious popup/wake-up "Settings / Content hidden" notifications & Settings crashes.

To my somewhat-trained debugging eye, it seems like Bluetooth state got corrupted and the OS thought the Bluetooth was off, while BT was really still turned on - thus the watch was trying to reconnect, prompting those popups and wakeups. But since the OS half-thought Bluetooth was off, the pairing request just caused a crash for Settings. Re-enabling BT (while it was physically still on) ended up corrupting and rebuilding the paired list, wiping it, and making everything work again.