I have four images, each 278×450, specified for the TG: Image Showcase. When viewing on an iPhone in portrait orientation, the fourth image doesn’t display but the first one displays twice. The second image briefly displays and is replaced by the first.
Observing your website, it seems like you have made some changes in theme code. If that is the case then please revert back it’s code to original and check once. And post us back if your problem still persists.