Seems like a hardware issue to me. I've never had any of those on my 5x. I had a 5 that had to be replaced because it did have a hardware issue. Bad RAM can cause the symptoms you described, and I believe that was the problem with my 5.
I had this bad then uninstalled the FB app & Messenger and it all cleared up. Maybe coincidence with a OS update that I didn't register but many online said FB was major stability issues on 5X so worth a try!
I've gotten the exact same thing. Also hoping it clears up
> Developer Preview 2 is intended for developers and not as a daily driver; this build is not yet optimized for performance and battery life.