It's Google Play Service. Check your Google account from settings. If there's other google account login. Log it out.
I had the same problem. I deleted two Google accounts I had in the device and it went away.
Sony Bravia x900f -- this box appears during any app that is being used as well as when the Nintendo switch is streaming through the TV.
Any ideas?
It went away for me, only after a factory reset.
Nothing else worked for me. I feel your pain.
Try KillApps too, and that way you should be able to tell if it is an app, before deleting them all one by one
https://play.google.com/store/apps/details?id=com.tafayor.killall
is that supposed to be black?
Keep deleting apps until it goes away. Tell us which app caused it.