Settings / Projector / Lightbox / Thumbnail strip / Fixed shape filter = OFF
Other than this the skin crops the extremes: horizontally the images wider than 3.33 : 1 and taller than 0.75 : 1 aspect ratio. This is necessary in order to get a wide enough thumbnail to be able to tap on mobiles, and also restricts the extreme panoramas, because they could occupy the full width of the thumbnail strip otherwise.
If you still sure you want to allow these fire up skin editor with Ctrl-Shift-E and comment out the following line (1016) in init.js:
// engine.addFilter(new ConstrainRatioFilter(0.75, 3.33333), JAFilter.THUMBNAILS_PRESCALE_STAGE);