Made a new ship with thicker walls.  Epoxied the trouble spots.

It seemed to shrink less.  Then the nose started sagging along the Z seam, where it under extruded.

So that was a 3rd trouble spot, but it's never going to be completely bulletproof as long as it's made of PETG.

Made the final movie about it.  Some window sections always shrink, but it's less garish.

The windows actually diffuse the upward smoke, emphasizing the backflow smoke in ways other incense burners don't.  All the other incense burners have the upward smoke fully exposed.