Not all of the polyobject flats are rendered in ACZ1

Not major, but might as well fix it now that we can.

Known, and not sure if they'll be fixed. Polyobject flats are still somewhat glitchy and need a particular setup to work flawlessly (in particular, multiple polyobjects in a sector with flats bugs out), so the update only applied flats to the platform part since it's the most important to the viewer.