Some Nexus Trays are displaying upside down. See attached. Shows OK in preview, but upside down in actual display.

That's actually normal. Some themes only have a bitmap for a bottom dock, so Nexus automatically flips and mirrors the bitmap as needed to match the current dock's orientation (horizontal bottom, horizontal top, vertical left, vertical right).

The theme preview screen always shows a dock at the bottom, but the dock on your screen is a top dock. So the bitmap gets flipped as it should.

You can disable this behavior for docks at the top by enabling the 'Do not flip background for docks at the top of the screen' setting in the Position tab of the Dock Properties dialog.

Thanks! That fixed it.