Sudden shift of focal direction when placing blocks

When placing blocks (tested with stone, dirt, and clay brick blocks), random times my screen very briefly flashes, and then I am facing 90 deg or 180 deg off from my original focal point.    Sometimes I am turned AND facing down.  

I use crosshair focal point indicator, so I know exactly where I am facing and placing blocks.

Private world, 1 tablet tested.  I will test on a 2nd tablet this evening, and on my Realm, once MC fixes it.