What can I do to stop Touch Bar overflowing to bottom of screen? My system:

MacBook Pro (15inch 2016)
Sierra 10.12.5.

has suddenly started exhibiting some unusual behaviour.
The only thing that I've done lately in the settings was in relation to Accessibility and Zoom.
I can't see how that has made the Touch Bar overflow into the bottom of the screen as well. Like so:

Does anyone know what I need to do to undo this?
Thanks.
Found the answer here:
https://support.apple.com/en-gb/HT207258
I think there must be a Mac bug.
I had never used Switch Control. It was off. But by switching it on then toggling the Switch Bar on and off via the Switch Control Home Panel > System I managed to finally disable the annoying thing.